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PREFACE 


Id  introducing"  this  book  to  American  Builders  and 
others  who  are  interested  in  the  use  of  plasters,  stuccos, 
cements  and  mortar,  I  feel  that  I  am  doing  them  a 
service,  as  there  is  no  such  work,  so  far  as  I  have  been 
able  to  discover,  published  in  this  country  that  appeals 
so  directly  to  the  practical  workman  as  the  present  vol- 
ume does;  as  I  have  endeavored  to  put  together  as  much 
practical  stuff  as  it  was  possible  to  wedge  in  in  a  vol- 
ume of  this  size,  and  in  order  to  do  this,  I  have  gleaned 
the  best  things  I  could  find  in  English,  American  and 
other  books  and  journals,  to  which  I  have  added  much 
drawn  from  my  own  experience,  and  from  the  experi- 
ences of  many  practical  workmen.  I  have  particularly 
drawn  at  length  from  Miller's  exhaustive  work  on  the 
subject  of  plastering  and  stucco  work,  and  am  also 
indebted  to  the  same  source  for  a  number  of  illustra- 
tions used  in  PART  ONE.  I  have  also  drawn  from 
Robert  Scott  Burns  to  some  small  extent,  and  from  an 
earlier  work  of  my  own,  and  from  articles  I  have  fur- 
nished to  various  building  journals  during  the  last 
thirty  years.  Part  Two  is  made  up  partly  from  my 
own  experience,  and  partly  from  treatises  on  cements 
and  concretes,  and  from  Government  Bulletins  pub- 
lished in  Washington,  D.  C.  The  paragraphs  and  illus- 
trations on  reinforced  concrete  are  mostly  taken  from 
reports  of  scientific  societies,  and  from  papers  read 
before  conventions,  and  from  letters  and  descriptions 
prepared  by  manufacturers  and  users  of  Portland  ce= 

5 


188^8 


6 


CEMENTS  AND  CONCRETES 


ment,  furnished  me  on  application,  and  from  materials 
gathered  from  many  sources,  and,  while  I  have  added 
considerable  from  my  own  knowledge  of  the  sabject, 
it  may  be  said  that  the  work  is  almost  a  compilation 
taken  from  the  best  authorities  on  the  subjects  dis- 
cussed. 

There  is  enough  material  on  the  subject  of  concrete 
floating  about  in  the  technical  press,  of  the  best  kind, 
to  build  up  three  or  four  volumes  of  the  size  of  this 
one,  but,  in  analyzing  it,  I  have  sifted  it  down  to  the 
limits  of  this  book,  preserving  that,  which  in  my  judg- 
ment, was  best  for  the  practical  worker,  and  leaving  out 
the  most  of  that  which  might  be  termed  theoretical  and, 
therefore,  to  a  large  extent  unfit  for  artisans'  purposes. 
In  making  the  selections  in  matters  of  this  kind,  the 
personal  factor  must  necessarily  be  of  more  or  less 
value,  and  I  flatter  myself  that,  after  a  successful  build- 
ing experience  in  various  forms,  covering  a  period  of 
over  fifty  years,  my  knowledge  of  the  value  of  any 
problem  pertaining  to  the  building  trades  is  deserving 
of  considerable  respect.  It  is  this  knowledge,  along 
with  some  knowledge  of  cause  and  effect,  and  my  simple 
and  unvarnished  methods  of  placing  building  matters 
before  the  American  workmen,  that  have  made  my 
books  so  popular,  and  lured  the  working  public  into  pur- 
chasing, at  this  writing,  nearly  two  millions  of  them. 
And  I  have  reason  to 'hope  that  this  volume  will,  like 
all  my  previous  ones,  meet  with  a  reasonable  amount 
of  appreciation  from  those  who  work,  or  guide  the  work 
of  others,  in  cements,  plasters,  concretes  and  stuccos. 

Fred  T.  Hodgson. 


PART  I 


CONCRETES,  CEMENTS,  PLASTERS  AND  STUC- 
COS— THEIR  USES  AND  METHODS 
OF  WORKING  SAME. 

INTRODUCTORY 

This  book,  or  rather  compilation,  is  largely  made  up 
of  the  very  best  material  available  on  the  subjects  it 
proposes  to  discuss.  All  the  latest  improvements  and 
methods  in  the  mixing,  proportioning  and  application 
of  plaster,  mortar,  stucco  and  cement  will  be  described 
and  laid  before  the  reader  in  as  simple  and  plain  a  man- 
ner as  possible. 

The  art  of  using  mortars  in  some  shape  or  other,  is 
as  old  as  civilization,  as  we  find  evidences  of  its  use  in 
ruins  that  date  long  before  historical  times,  not  only 
in  the  older  countries  of  Asia  and  Europe,  but  also  in 
the  ruins  of  Mexico,  Central  America  and  Peru;  and 
the  workmen  who  did  their  part,  or  most  of  this  work, 
were  evidently  experts  at  the  trade,  for  some  of  the 
remains  of  their  work  which  have  come  down  to  us 
certainly  show  that  the  work  was  done  by  men  who 
not  only  had  a  knowledge  of  their  trade,  but  that  they 
also  possessed  a  fair  knowledge  of  the  peculiar  qualities 
of  the  materials  they  used.  '^Plastering,"  says  Miller 
in  his  great  work  on  Mortars,  "is  one  of  the  earliest 
instances  of  man's  power  of  inductive  reasoning,  for 
when  men  built  they  plastered:  at  first,  like  the  birds 
and  the  beavers,  with  mud;  but  they  soon  found  out  a 
more  lasting  and  more  comfortable  method,  and  the 

7 


8 


CEMENTS  AND  CONCRETES 


earliest  efforts  of  civilization  were  directed  to  plaster- 
ing. The  inquiry  into  it  takes  us  back  to  the  dawn  of 
social  life  until  its  origin  becoraes  mythic  and  prehis- 
toric. In  that  dim,  obscure  period  Ave  cannot  pene- 
trate far  enough  to  see  clearly,  but  the  most  distant 
glimpses  we  can  obtain  into  it  show  us  that  man  had 
very  early  attained  almost  to  perfection  in  compound- 
ing material  for  plastering.  In  fact,  so  far  as  we  yet 
know,  some  of  the  earliest  plastering  which  has  re- 
mained to  us  excels,  in  its  scientific  composition,  that 
which  we  use  at  the  present  day,  telling  of  ages  of  ex- 
perimental attempts.  The  pyramids  of  Egypt  contain 
plaster  work  executed  at  least  four  thousand  years  ago 
(some  antiquaries,  indeed,  say  a  much  longer  period), 
and  this,  where  wilful  violence  has  not  disturbed  it, 
still  exists  in  perfection,  outvying  in  durability  the 
very  rock  it  covers,  where  this  is  not  protected  by  its 
shield  of  plaster.  Dr.  Flinders  Petrie,  in  his  ^Pyra- 
mids and  Temples  of  Gizeh,'  shows  us  how  service- 
able and  intelligent  a  co-operator  with  the  painter,  the 
sculptor,  and  the  architect,  was  the  plasterer  of  those 
early  days,  and  that  to  his  care  and  skill  we  owe  almost 
all  we  know  of  the  history  of  these  distant  times  and 
their  art.  Indeed  the  plasterer's  very  tools  do  yet  re- 
main to  us,  showing  that  the  technical  processes  then 
Vv^ere  the  same  we  now  use,  for  there  are  in  Dr.  Petrie 's 
collection  hand  floats  which  in  design,  shape  and  pur- 
pose are  precisely  those  which"  we  use  today.  Even  our 
newest  invention  of  canvas  plaster  was  well  known 
then,  and  by  it  were  made  the  masks  which  yet  pre- 
serve on  the  mummy  cases  the  lineaments  of  their  occu- 
pants. ' ' 

The  plaster  used  by  the  Egyptians  for  their  finest 
work  was  derived  from  burnt  gypsum^  and  was  there- 


INTRODUCTORY 


9 


fore  exactly  the  same  as  our  ''plaster  of  paris.''  Its 
base  was  of  lime  stucco,  which,  when  used  on  partitions, 
was  laid  in  reeds,  laced  together  with  cords,  for  lath- 
ing, and  Mr.  Miller,  who  has  examined  a  fragment  in 
Dr.  Petrie's  collection,  finds  it  practically  ''three  coat 
work,"  about  %  of  an  inch  thick,  haired  and  finished 
just  as  we  do  now. 

Plaster  moulds  and  cast  slabs  exist,  but  there  does  not 
appear  any  evidence  of  piece  moulding,  nor  does  any 
evidence  of  the  use  of  modelled  work  in  plaster  exist. 
That  some  process  of  indurating  plaster  was  thus  early 
known  is  evidenced  by  the  plaster  pavement  at  Tel-el 
Amarna,  which  is  elaborately  painted.  The  floor  of 
this  work  is  laid  on  brick;  the  first  coat  is  of  rough 
lime  stucco  about  1  inch  thick,  and  the  finishing  coat 
of  well-haired  plaster  about  %  inch  thick,  very  smooth 
and  fine,  and  showing  evidence  of  trowelling,  the  set- 
ting out  lines  for  the  painting  being  formed  by  a  struck 
cord  before  the  surface  was  set,  and  the  painting  done 
on  fresco.  It  is  about  60  by  20,  and  formed  the  floor 
of  the  principal  room  of  the  harem  of  King  Amenhotop 
IV.,  about  fourteen  hundred  years  before  Christ,  that 
is,  between  three  thousand  and  four  thousand  years 
ago.  Long  before  this,  plastering  of  fine  quality 
existed  in  Egypt,  and  so  long  as  its  civilization  con- 
tinued it  aided  the  comfort  of  the  dwellings  of  its 
people  and  the  beauty  of  its  temples. 

Nor  was  it  merely  for  its  beauty  and  comfort  that 
plaster  work  was  used.  Even  then  its  sanitary  value 
was  recognized,  and  the  directions  given  in  Leviticus 
xiv,  42-48,  which  was  probably  written  about  one  hun- 
dred years  before  this  date,  show  that  the  knowledge 
of  its  antiseptic  qualities  was  widely  spread^  and  the 
practice  of  it  regarded  as  religious  duty. 


10  CEMENTS  AND  CONCRETES 


Unfortunately  there  is  no  direct  evidence  that  the 
adjacent  Assyrian  powers  of  Nineveh  and  Babylon  nsed 
plaster  work.  Possibly  the  fine  clay  brought  down  by  the 
rivers  of  the  Euphrates  and  the  Tigris  sufficed  for  all 
their  purposes.  Their  records  are  in  it :  their  illustra- 
tions on  the  sculptured  walls  of  their  palaces  are  in 
stone,  their  painting  is  glazed  on  their  bricks,  and  for 
them  there  seems  to  have  been  but  little  need  for  plas- 
ter work,  nor  do  we  find  until  the  rise  of  Grecian  art 
anything  relating  to  our  subject. 

Very  early  in  Greek  architecture  we  find  the  use  of 
plaster,  and  in  this  case  a  true  lime  stucco  of  most  ex- 
quisite composition,  thin,  fine  and  white.  Some  has 
been  found  at  Mycenae,  a  city  of  Homeric  date.  We 
know  that  it  existed  in  perfection  in  Greece  about  five 
hundred  years  before  the  Christian  era.  With  this  the 
temples  were  covered  externally,  and  internally  where 
they  were  not  built  of  marble,  and  in  some  cases  where 
they  were.  This  fine  stucco  was  often  used  as  a  ground 
on  which  to  paint  their  decorative  ornament,  but  not 
infrequently  left  quite  plain  in  its  larger  masses,  and 
some  of  it  remains  in  very  fair  preservation  even  to 
this  day.  The  Temple  of  Apollo  at  Bassae,  built  of 
yellow  sandstone  about  470  B.  C,  has  on  its  columns 
the  remains  of  a  fine  white  stucco. 

Pavements  of  thick,  hard  plaster,  stained,  of  various 
colors,  were  common  in  the  Greek  temples.  One  of 
these,  that  of  the  Temple  of  Jupiter  Panhellenius  at 
^gina,  built  about  570  B.  C,  is  described  by  Cockerell 
as  existing  in  the  early  part  of  the  century,  in  good 
condition,  though  the  temple  itself  was  destroyed  ;  and 
I  have  seen  at  Agrigentum  plaster  existing  in  perfect 
state,  though  scarcely  thicker  than  an  egg-shell,  on  the 
sheltered  parts  of  a  temple  built  at  least  three  hundred 


INTRODUCTORY 


11 


/ears  before  our  era,  whilst  the  unprotected  stone  was 
weather  worn  and  decayed. 

What  care  the  ancient  Greeks  bestowed  on  their 
stucco  may  be  inferred  from  Pliny's  statement  that  in 
the  temple  at  El:s  about  450  B.  Panaenus,  the 
nephew  of  Phidias,  used  for  the  groundwork  of  his 
picture  stucco  mixed  with  milk  and  saffron,  and  pol- 
ished with  spittle  rubbed  on  by  the  ball  of  the  thumb, 
and,"  says  he^  ^'it  still  retains  the  odor  of  saffron/' 
Lysippus,  the  first  of  the  Greek  '^realists"  in  sculpture, 
was  the  first  we  hear  of  who  took  casts  of  the  faces  of 
living  sitters  about  300  B.  C,  so  the  art  of  plaster  cast- 
ing must  have  advanced  a  good  deal  by  that  time,  as  he 
made  presents  of  copies  to  his  friends.  Afterwards  we 
read  of  many  sculptors  who  sent  smaller  plaster  models 
of  their  works  to  friends.  These  were,  however,  prob- 
ably carved  in  the  plaster  rather  than  cast. 

Whether  the  Greeks  used  stucco  for  modelling  is  a 
somewhat  doubtful  point  amongst  antiquarians.  From 
certain  passages  in  classic  writers  I  am  induced  to  think 
they  did.  Pausanius,  who  describes  the  temple  at  Stym- 
phalus,  an  almost  deserted  and  ruined  city  when  he 
visited  it  about  130  A.  D.,  describes  the  ceiling  of  the 
Temple  of  the  Stymphalides,  built  about  400  B.  C,  as 
being  either  of  stucco  or  carved  wood,"  he  could  not 
decide  which,  but  his  very  doubt  would  imply  that 
stucco  or  wood  were  equally  common.  Now,  this  ceil- 
ing was  ornamented  with  panels  and  figures  of  the 
harpies — omens  of  evil,  half  woman  and  half  bird,  with 
outspread  wings.  He  also  mentions  a  statue  of  Bac- 
chus in  '^colored  stucco."  Of  course  these  are  not  defi- 
nite proofs  of  early  Greek  stucco  modelling,  but  as  the 
city  of  Stymphalus  had  decayed  and  become  depopu- 
lated before  200  B.  C,  there  is  certainly  presumptive 


12 


CEMENTS  AND  CONCRETES 


evidence  of  the  ancient  practice  of  the  art.  Again,  fig- 
ures of  unburnt  earth  are  mentioned  in  contradistinc- 
tion to  those  of  terra  cotta,  and  sundry  other  allusions 
to  plastic  work  occur,  which  lead  me  to  the  opinion  that 
quite  early  in  Greek  art  this  mode  of  using  plaster  be- 
gan. At  any  rate,  we  know  that  it  was  early  introduced 
into  Grecia  Magna — the  earliest  Southern  Italian  col- 
ony of  the  Greeks;  and  as  colonists  invariably  preserve 
the  customs  and  traditions  of  their  fatherland  even  long 
after  they  have  fallen  into  disuse  in  their  native  hom.e, 
we  can  have  no  reasonable  doubt  but  this  art  was  im- 
ported rather  than  invented  by  them.  Thence  it  spread 
to  the  Etruscans  of  Middle  Italy,  a  cognate  people  to 
the  Southern  Greeks,  by  whom  both  plain  and  modelled 
stucco  was  largely  used.  The  Etruscans,  as  we  have 
seen,  were  more  closely  allied  to  the  Greek  than  the 
Latin  race,  but  in  the  course  of  time  these  two  races 
amalgamated,  the  former  bringing  skill  in  handicraft, 
the  latter  lust  of  power,  and  patriotic  love  of  country 
and  of  glory,  whilst  the  Grecian  element,  which  blended 
harmoniously  with  the  first  of  these,  added  a  love  of  art. 

This  union,  however,  took  long  to  ripen  to  artistic 
fruitfulness.  The  practical  Etruscan  element  firstly 
constructed  the  roads  and  the  sewers,  and  gave  health  to 
Rome.  The  Latins  added  to  their  territory  until  it  em- 
braced half  of  Europe,  giving  wealth  to  Rome,  and  not 
till  the  luxury  and  comfort  thus  created  did  the  artis- 
tic element  of  the  Greek  come  in,  giving  beauty  to 
Rome,  and  the  day  of  decorative  plaster  work  ap- 
proached its  noontide  glory,  making  Rome  the  attrac- 
tion of  the  world.  The  absorbance  of  Greece  as  a 
Roman  province  took  place  B.  C.  145,  and  the  loot  of 
it  began,  giving  an  enormous  impetus  to  Roman  art. 
Thousands  of  statues  were  brought  to  Rome,  and  to 


INTRODUCTORY 


be  deemed  a  connoisseur  in  things  artistic  or  a  patron 
of  the  arts  became  the  fashionable  ambition.  But  it 
was  not  until  the  century  just  preceding  the  Christian 
era  that  it  became  especially  noteworthy.  Of  course 
there  is  hardly  anything  left  to  us  of  the  very  early 
plaster  w^ork  of  Rome.  The  constant  search  for  some 
new  thing  was  inimical  to  the  old.  Old  structures  were 
pulled  down  to  make  way  for  new,  which  in  their  turn 
gave  way  to  newer,  and  until  the  age  of  Augustus  we 
have  but  little  of  the  early  work  left.  Strabo,  who 
visited  Rome  about  this  time,  complains  of  the  destruc- 
tion caused  by  the  numerous  fires,  and  continued  pull- 
ing  down  of  houses  rendered  necessary,  for  even  pulL 
ing  down  and  rebuilding  in  order  to  gratify  the  taste 
is  but  voluntary  ruin;  and  Augustus,  who  boasted  that 
*'he  found  Rome  of  brick  and  left  it  of  marble,"  in 
replacing  the  brick  with  marble  destroyed  the  plaster 
work.  How  that  plaster  work  was  wrought  we  shall 
learn  more  from  Vitruvius,  who  wrote  his  book  on  archi- 
tecture about  16  B.  C,  and  dedicated  it  to  the  emperor, 
^'in  order  to  explain  the  rules  and  limits  of  art  as  a 
standard  by  which  to  test  the  merits  of  the  buildings 
he  had  erected  or  might  erect." 

Now,  Vitruvius  was  a  man  who  had  travelled  and 
seen  much.  He  was  with  Julius  Caesar  as  a  military 
engineer  in  his  African  campaign  in  46  B.  C,  or  ten 
years  after  Caesar's  invasion  of  Britain.  Afterwards 
he  became  a  designer  of  military  engines,  what  we 
should  caJl  head  of  the  Ordnance  Department,  and  also 
a  civil  engineer,  persuading  him^self  that  he  had  a 
pretty  taste  in  architecture,  just  as  though  he  were  an 
R.  E.  of  today.  Thus  he  had  a  practical  and  also  an 
artistic  training,  and  here  is  what  he  says  on  matters 
connected  with  plaster  work  in  Book  VII,  Chapter  IL 


14 


CEMENTS  AND  CONCRETES 


On  tempering  lime  for  stucco  :  ^  ^  This  requires  that  the 
lime  should  be  of  the  best  quality,  and  tempered  a  long 
time  before  it  is  wanted  for  use;  so  that  if  any  of  it  be 
not  burnt  enough,  the  length  of  time  employed  in  slak- 
ing it  may  bring  the  whole  mass  to  the  same  consist- 
ency." He  then  advises  it  to  be  chopped  with  iron 
hatchets,  adding  that  ''if  the  iron  exhibits  a  glutinous 
substance  adhering  to  it,  it  indicates  the  richness  of  the 
lime,  and  the  thorough  slaking  of  it.''  For  cradling 
out,  and  for  ceiling  joists,  he  recommends  ''the  wood 
to  be  of  cypress,  olive,  heart  of  oak,  box  and  juniper,"  as 
neither  is  liable  to  "rot  or  shrink."  For  lathing  he  speci- 
fies "Greek  reeds  bruised  and  tied  with  cords  made  from 
Spanish  broom,"  or  if  these  are  not  procurable  "marsh 
reeds  tied  with  cords."  On  these  a  coat  of  lime  and 
sand  is  laid,  and  an  additional  coat  of  sand  is  laid  on 
to  it.  As  it  sets  it  is  then  polished  with  chalk  or  marble. 
This  for  ceilings.  For  plaster  on  wall  he  says :  "  The 
first  coat  on  the  walls  is  to  be  laid  on  as  roughly  as 
possible,  and  while  drying,  the  sand  and  coat  spread 
thereon.  When  this  work  has  dried,  a  second  and  a 
third  coat  is  laid  on.  The  sounder  the  sand  and  coat  is, 
the  more  durable  the  work  will  be.  The  coat  of  marble 
dust  then  follows,  and  this  is  to  be  so  prepared  that 
when  used  it  does  not  stick  to  the  trowel.  Whilst  the 
stucco  is  drying,  another  thin  coat  is  to  be  laid  on :  this 
is  to  be  well  worked  and  rubbed,  then  still  another, 
finer  than  the  last.  Thus  with  three  coats  and  the 
same  number  of  marble  dust  coats  the  walls  will  be 
solid,  and  not  liable  to  crack.  The  wall  that  is  well 
covered  with  plaster  and  stucco,  when  well  polished, 
not  only  shines,  but  reflects  to  the  spectators  the  images 
falling  on  it.  The  plasterers  of  the  Greeks  not  only 
make  their  stucco  work  hard  by  adhering  to  these  direc- 


INTRODUCTORY 


15 


tions,  but  when  the  plaster  is  mixed,  cause  it  to  be  beat- 
en with  wooden  staves  by  a  great  number  of  men,  and 
use  it  after  this  preparation.  Hence  some  persons  cut- 
ting slabs  of  plaster  from  ancient  walls  use  them  for 
tables  and  mirrors/'    (Chapter  III.) 

You  will  see  by  these  remarks  the  great  care  taken 
through  every  process,  and  how  guarded  the  watchful- 
ness over  the  selection  of  materials,  and  you  will  also 
note  the  retrospectiveness  of  Vitruvius'  observation, 
how  he  felt  that  the  work  done  before  the  frantic  haste 
of  his  own  time  was  the  better:  very  much  as  we  find 
now.  Time  is  an  ingredient  in  all  good  work,  and  its 
substitute  difficult  to  find. 

There  are  other  tips''  contained  in  this  work  which 
are  worth  extraction,  as,  for  instance,  his  instructions 
as  how  to  plaster  damp  walls.  In  such  case  he  prima- 
rily suggests  a  cavity  wall,  with  ventilation  to  insure 
a  thorough  draught,  and  then  plastering  it  with  pot- 
sherd mortar, ' '  or  carefully  covering  the  rough  plaster 
with  pitch,  which  is  then  to  be  ^^lime  whited  over,"  to 
insure  ^'the  second  coat  of  pounded  potsherds  adhering 
to  it,"  when  it  may  be  finished  as  already  described. 
Further,  he  refers  to  modelled  plaster  work  which,  he 
says,  ought  to  be  used  with  a  regard  to  propriety," 
and  gives  certain  hints  for  its  appropriate  use.  Speak- 
ing of  pavements  ^^used  in  the  Grecian  winter  rooms, 
which  are  not  only  economical  but  useful,"  he  advises 
''the  earth  to  be  excavated  about  two  feet,  and  a  foun- 
dation of  potsherd  well  rammed  in,"  and  then  a  ^^com- 
position of  pounded  coal  lime,  sand  and  ashes  is  mixed 
up  and  spread  thereover,  half  foot  in  thickness,  per- 
fectly smooth  and  level.  The  surface  then  being  rubbed 
with  stone,  it  has  the  appearance  of  a  black  surface," 
^'and  the  people,  though  barefoot,  do  not  suffer  from 


16 


CEMENTS  AND  CONCRETES 


cold  on  this  sort  of  pavement.''  Now  all  this  bespeaks 
not  only  theoretical  knowledge,  but  practical  observa- 
tion and  experience,  and  was  written  nearly  two  thou- 
sand years  ago,  from  which  you  can  surmise  how  far 
advanced  practical  plastering  had  then  become.  This 
written  evidence  is  almost  all  we  have  of  the  work  of 
Vitruvius'  own  time,  for  even  of  the  time  of  Augustus 
hardly  anything  remains  to  us,  as  the  great  fire  of 
Nero  utterly  destroyed  the  greater  part  of  the  city  in 
the  year  A.  D.  64,  and  almost  the  only  authenticated 
piece  of  plaster  work  done  before  or  during  his  reign 
is  the  Tabula  Iliaca,  a  bas-relief  of  the  Siege  of  Troy, 
still  preserved  in  the  Capitol  Museum  at  Rome.  That 
this  was  modelled  by  Greek  artists  is  proved  by  the  fact 
that  its  inscriptions  are  all  in  the  Greek  language,  and 
by  some  it  is  considered  to  be  of  ver}^  much  greater  an- 
tiquity. So  much  for  the  ancient  history  of  the  art 
of  plastering,  and  I  trust  I  will  be  pardoned  if  I  con- 
tinue this  sketch,  bringing  it  down  to  a  more  recent 
period  and  show  in  what  high  respect  the  plasterers '  art 
was  held  in  the  Sixteenth  Century,  and  later.  Quoting 
from  an  old  work,  giving  an  account  of  the  institution 
of  ' '  The  Worshipful  Company  of  Plaisterers, ' '  and  mak- 
ing use  of  the  quaint  language  then  in  use  we  are  told 
that:  ^^The  Plaisterers'  Company,  which  ranks  as 
forty-sixth  among  the  eighty-nine  companies,  was  in- 
corporated by  King  Henry  VII.,  on  March  10,  1501,  to 
search,  and  try,  and  make,  and  exercise  due  search  as 
well  in,  upon,  and  of  all  manner  of  stuff  touching  and 
concerning  the  Art  and  Mystery  of  Pargettors,  com- 
monly called  Plaisterers,  and  upon  all  work  and  work- 
men in  the  said  art  or  mystery,  so  that  the  said  work 
might  be  just,  true,  and  lawful,  without  any  deceit  or 
fraud  whatsoever  against  the  City  of  London  or  suburbs 


INTRODUCTORY 


17 


thereof.  The  Charter  gave  power  to  establish  the  Corn- 
pany  as  the  Guild  or  Fraternity  in  honour  of  the 
Blessed  Virgin  Mary,  of  men  of  the  Mystery  or  Art  of 
Pargettors  in  the  City  of  London,  commonly  called 
Plaisterers,  to  be  increased  and  augmented  when  neces- 
sary, and  to  be  governed  by  a  Master  and  two  War- 
dens, to  be  elected  annually.  The  Master  and  Wardens 
and  brotherhood  were  to  be  a  Hody  corporate,  with  per- 
petual succession  and  a  common  seal,  and  they  were 
empowered  to  purchase  and  enjoy  in  fee  and  perpet- 
uity lands  and  other  possessions  in  the  City,  suburbs 
and  elsewhere.  And  the  charter  empowered  the  said 
Master  and  Wardens  to  sue  and  be  sued  as  ''The  Mas- 
ter and  Wardens  of  the  Guild  or  Fraternity  of  the 
Blessed  Mary  of  Pargettors,  commonly  called  Plaister- 
ers,  London.'' 


THE  OLD  COAT  OF  AILJIS. 


The  Company  under  the  powers  to  make  examina- 
tions, appears  to  have  inflicted  fines  on  offending  par- 
ties for  using  bad  materials,  and  for  bad  vvorkmanship. 
Search  days  appear  to  have  been  annually  appointed 
up  to  1832,  but  not  since,  and  the  Company  has  not 
exercised  any  control  over  Plaisterers'  work  for  many 
,year§, 


18  CEMENTS  AND  CONCRETES 


Another  charter  was  granted  by  Queen  Elizabeth  in 
1559,  but  it  has  been  lost,  and  there  is  no  record  of 
the  contents.  The  Queen  granted  a  new  charter  in 
1597,  which  confirmed  the  privileges  of  the  Company, 
and  extended  the  authority  of  the  Master  and  Wardens 
to  and  over  all  persons  exercising  the  art  of  plaisterers, 
as  well  English  as  aliens  and  denizens  inhabiting  and 
exercising  the  said  art  within  the  City  and  suburbs  and 
liberties,  or  within  two  miles  of  the  City. 


THE  PEESSNT  COAT  OP  ARMS, 


Charles  II.,  by  a  charter  dated  June  19,  1679,  con- 
firmed  the  privileges  granted  by  the  previous  charters. 
Having  in  view  the  rebuilding  of  the  City,  he  forbade 
any  person  to  carry  on  simultaneously  the  trades  of 
a  mason,  bricklayer  or  plaisterer,  or  to  exercise  or  carry 
on  the  art  of  a  plaisterer  without  having  been  appren- 
ticed seven  years  to  the  mystery.  The  jurisdiction  of 
the  Company  was  extended  to  three  miles'  distance 
from  the  City. 

There  were  two  orders  made  by  the  Court  of  Alder- 
men (exemplified  under  the  mayoralty  seal,  April  1) 


INTRODUCTORY 


19 


1585)  for  settling  matters  in  dispute  between  the  tilers 
and  bricklayers  and  the  plaisterers  as  to  interfering  in 
each  other's  trades.  The  observance  of  these  orders 
was  enforced  by  an  order  of  the  Privy  Council  dated 
June  1,  1613,  and  a  general  writ  or  precept  issue  to  the 
*  same  effect  on  August  13,  1613. 


Indian  Centre-Piece. 


There  was  also  an  order  of  the  Court  of  Aldermen 
(29  Elizabeth,  February  14,  1586-7)  relating  to  the 
number  of  apprentices  to  be  kept  by  members. 

An  act  of  Common  Council  was  passed,  under  date 
of  18  James  I.,  October  5,  1620. 

An  act  of  Common  Council  (6  "William  and  Mary, 
October  19,  1694)  was  also  passed  to  compel  all  persons 
using  the  trade  of  plaisterer  in  the  City  of  London,  or 


20 


CEMENTS  AND  CONCRETES 


the  liberties  thereof,  to  become  free  of  the  Company 
under  penalty  to  be  recovered  as  therein  mentioned.  In 
the  East  the  Art  of  ornamental  plastering  was  well 
known  and  almost  universally  practiced  before  Mahom- 
et established  a  new  order  of  things,  and  the  enriched 
plaster  work  of  India,  Persia  and  other  Eastern  Em- 
pires are  evidences  of  the  high  character  of  the  work- 
manship of  the  Oriental  workers  in  plaster.  The 
Arabian  and  Moor  brought  back  the  Art  of  the  Western 
World  in  the  early  part  of  the  thirteenth  century, 
and  it  is  to  them  we  owe  the  splendid  plaster  work  of 
the  Alhambra  and  other  work  still  in  existence  in  Spain. 
In  the  Mosque  at  Medina,  built  in  622,  are  still  to  be 
seen  some  fine  specimens  of  old  plaster  work  that  was 
wrought  on  the  building  at  the  time  of  its  completion. 
The  Mosque  of  Ibu-tubun,  Cairo,  Egypt,  which  was  fin- 
ished in  A.  D.  878,  abounds  with  beautiful  plaster  work. 
It  contains  a  number  of  arches  and  arcades,  the  capi- 
tals of  which,  like  the  rest  of  the  building,  are  enriched 
wdth  plaster  buds  and  flowers  made  in  elaborate  de- 
signs. Even  in  Damascus,  thai  old  and  far-off  City 
indulged  in  ornamental  plaster-work  when  the  people 
of  Western  Europe  were  cutting  one  another's  throats 
for  political  ascendency.  We  illustrate  a  few  examples 
of  old  work  taken  from  existing  specimens.  These  will 
to  some  extent,  give  an  idea  of  what  the  old  plasterers 
could  do.    See  illustrations  attached. 

During  the  middle  ages  in  Europe  plastering  and 
stucco  existed  only  as  a  craft,  and  its  highest  function 
was  to  prepare  a  surface  to  be  painted  on.  Sometimes 
it  was  used  as  an  external  protection  from  the  weather 
but  rarely  was  it  employed  for  direct  ornament.  Some- 
times small  ornaments  were  carved  in  plaster  of  Paris, 
but  it  played  no  important  part  in  decorative  Art, 


INTRODUCTORY 


21 


excepting  perhaps,  as  gesso,  though  this  belonged  rather 
to  the  painter  than  the  plasterer.  Nor  was  it  until  the 
commencement  of  the  Renaissance  in  Italy  that  it 
showed  any  symptoms  of  revival. 


■Arabesoue  from  the  Great  Mos^iUE,  Damascus. 


With  the  commencement  of  the  fifteenth  century  old 
learning  and  old  arts  began  to  be  studied,  the  discovery 
of  the  art  of  printing  and  the  consequent  multiplication 
of  the  copies  of  the  lore  heretofore  looked  up  in  old 
manuscripts   gave   invention   and   progress  new  life, 


22 


CEMENTS  AND  CONCRETES 


which  has  lasted  until  the  present  day.  Italy  has  al- 
ways been  the  nursing  mother  of  plasterers,  and  in  Mr. 
G  T.  Robinson's  ''Glimpse  of  the  History  of  the  Art 
and  Craft/'  he  has  shown  something  of  her  great  and 
glorious  past,  and  how  she  sent  her  sons  over  almost 
all  Europe  to  raise  the  art  and  status  of  this  craft. 


Persian  Centre- Pifxe. 


Even  during  the  depressing  times  of  her  history  she 
religiously  preserved  its  ancient  traditions  and  pro- 
cesses, and  in  almost  all  her  towns  there  was  some  one 
or  two  plasterers  to  whom  was  confided  the  restoration, 
the  repair  and  the  conservation  of  its  frescoes  or  its 
stuccos.  The  art  dwindled,  but  it  survived.  So  late 
as  1851  an  English  architect,  when  sketching  in  the 


INTRODUCTORY 


23 


Campo  Santo  at  Pisa,  found-  a  plasterer  busy  in  lov- 
ingly repairing  portions  of  its  old  plaster  work,  which 
cime  and  neglect  had  treated  badly,  and  to  whom  he 
applied  himself  to  learn  the  nature  of  the  lime  he  used. 
So  soft  and  free  from  caustic  qualities  w^as  it  that  the 
painter  could  work  on  it  in  true  fresco  painting  a  few 
days  or  hours  after  it  was  repaired,  and  the  modeller 
used  it  like  clay.  But  until  the  very  day  the  architect 
was  leaving  no  definite  information  could  he  extract. 
At  last,  at  a  farewell  dinner,  when  a  bottle  of  wine 
had  softened  the  way  to  the  old  man's  heart,  the  plas- 
terer exclaimed,  ^^And  now,  signor,  I  will  show  you 
my  secret!"  And  immediately  rising  from  the  table, 
the  two  went  off  into  the  back  streets  of  the  town,  when, 
taking  a  key  from  his  pocket,  the  old  man  unlocked  a 
door,  and  the  two  descended  into  a  large  vaulted  base- 
ment, the  remnant  of  an  old  palace.  There  amongst 
the  planks  and  barrows,  the  architect  dimly  saw  a  row 
of  large  vats  or  barrels.  Going  to  one  of  them,  the  old 
man  tapped  it  with  his  key;  it  gave  a  hollow  sound 
until  the  key  nearly  reached  the  bottom.  There,  sig- 
nor! there  is  my  grandfather!  he  is  nearly  done  for.'' 
Proceeding  to  the  -next,  he  repeated  the  action,  saying : 
'  ^  There,  signor !  there  is  my  father !  there  is  half  of  him 
left."  The  next  barrel  was  nearly  full.  That's  me! 
exclaimed  he;  and  at  the  last  barrel  he  chuckled  at 
finding  it  more  than  half  full:  ''That's  for  the  little 
ones,  signor!"  Astonished  at  this  barely  understood 
explanation,  the  architect  learned  that  it  was  the  cus- 
tom of  the  old  plasterers,  whose  trade  descended  from 
father  to  son  for  many  successive  generations,  to  care- 
fully preserve  any  fine  white  lime  produced  by  burning 
fragments  of  pure  statuary,  and  to  each  fill  a  barrel  for 
his  successors.     This  they  turned  over  from  time  to 


24  CEMENTS  AND  CONCRETES 


time,  and  let  it  ain — slake  in  the  moist  air  of  the  vault, 
and  so  provide  pure  old  lime  for  the  future  by  which 
to  preserve  and  repair  the  old  works  they  venerated. 
After-inquiries  showed  that  this  was  a  common  prac- 


PoRTiON  OF  A  Ceiling  from  Teheran,  Persia. 


tice  in  many  an  old  town,  and  thus  the  value  of  old 
air-slaked  lime,  such  as  had  been  written  about  eighteen 
hundred  years  before,  was  preserved  as  a  secret  of  the 
trade  in  Italy,  whilst  the  rest  of  Europe  was  advocating 


INTRODUCTORY 


25 


the  exclusive  use  of  newly  burnt  and  hot  slaked  lime. 
Was  there  in  the  early  part,  indeed  even  in  the  middle 


DiArFKED  Pi  aster  I'anei  i  int.  in  riiE  Aihamuka,  Sprain,  Thiriff-MH  Cf.nturv.  i 


of  the  present  century,  any  plaster  image  seller  who  was 
not  an  Italian?    Indeed,  at  this  present  time^  almost 


26 


CEMENTS  AND  CONCRETES 


all  the  *  ^  f ormatore ' '  or  piece  moulders  for  the  majority 
of  the  sculptors  of  Europe  are  of  Italian  nationality  or 
descent,  and  chiefly  by  these  has  the  national  craft  been 
maintained. 

When  after  the  long  European  wars  of  the  eighteenth 
and  the  commencement  of  the  nineteenth  century  Italy 
had  rest  and  power  to  ^^make  itself"  (faro  de  se),  the 
first  revival  of  its  industry  was  felt  by  her  plasterers, 
and  as  there  was  then,  as  now,  more  workmen  than 


Plastkr  Frieze  in  Mosque  of  Sultan  Hasan.  Fourteenth  Century. 


work,  they  emigrated  to  the  neighboring  countries;  and 
the  major  part  of  the  plasterers  along  the  Revieda,  in 
the  southern  provinces  of  Germany  and  Austria,  are 
Italians  who  go  off  with  and  return  with  the  swallows, 
to  earn  that  wage  the  poverty  of  their  own  country 
cannot  afford  them.  With  this  brief  historical  sum- 
mary I  conclude  the  Introductory  notice,  and  will  now 
pass  on  to  the  more  practical  domain  of  the  Plasterers' 
Art. 


MATERIALS. 


IJMES,   CEMENTS^   MORTARS^   SAND,   PLASTERS  AND  LATHS. 

LIMES. 

The  Lime  Principally  Used  for  internal  plastering 
is  that  calcined  from  carbonate  of  lime,  in  v/hich  the 
impurities  do  not  exceed  6  per  cent.,  and  is  known  as 
fat  lime,  pure  lime  or  rich  lime.  It  is  unfit  for  any 
purpose  where  strength  is  required,  or  in  situations 
where  it  is  exposed  to  the  weather,  as  it  has  no  setting 
power,  and  is  easily  dissolved  by  wet. 

Hydraulic  Limes  are  those  which,  in  order  to  set,  do 
not  require  any  outside  influences,  their  own  chemical 
composition  of  lime  and  silica^  when  burnt,  being  suf- 
ficient for  the  purpose.  The  name  is  given  for  their 
capability  of  setting  and  hardening  under  water.  Hy- 
draulic limes  are  obtained  mostly  from  the  lias. 

Good  Hydraulic  Limes  are  obtained  from  many 
places  in  the  United  States  and  Canada,  the  best 
known  is  ^^The  Rosendale  Hydraulic  Cement.'' 

Artificial  Hydraidic  Limes  may  be  made  by  mixing 
a. sufficient  quantity  of  clay  with  pure  lime  to  obtain 
a  composition  like  that  of  a  good  natural  hydraulic 
limestone.  The  lime^  if  soft,  may  be  mixed  with  the 
clay  and  burnt  raw,  or,  as  is  more  usual,  may  be  burnt, 
slaked,  ground,  and  then  mixed  with  the  clay  and  re- 
burnt. 

The  Purer  the  Lime  the  quicker  will  it  slake.  Great 
care  should  be  taken  that  the  lime  is  properly  burnt 
or  otherwise  it  will  not  slake  properly,  and  will  prob- 
ably ''blow''  in  the  work. 

27 


28 


CEMENTS  AND  CONCRETES 


The  Perfect  Slaking  of  the  burnt  lime  before  being 
^jsed  is  very  important,  as  it  will  slake  eventually,  and 
cause  blisters  in  the  work.  In  order  to  effect  thorough 
slaking,  the  lime  should  be  ^'run"  as  soon  as  the  build- 
ing is  commenced.  It  should  not  be  used  unless  it  has 
been  slaked  at  least  three  weeks. 

A  Bushel  of  Lime  requires  in  slaking  about  a  gallon 
and  a  half  of  water. 

Lime  which  Slakes  Quickly  and  with  great  heat  is 
generally  considered  to  be  the  best  for  plasterers'  work. 

When  Lime  Falls  in  dry  weather  without  any 
sufficient  apparent  moisture,  it  is  considered  to  foretell 
rain. 

The  Lime  Should  Be  Run  in  couch  on  the  site,  where 
it  can  be  seen  by  the  architect.  Care  should  be  taken 
that  as  much  lime  is  run  as  is  required  for  the  whole 
of  the  building. 

The  Plasterer^  partly,  perhaps,  to  avoid  the  money 
outlay,  and  partly  to  avoid  the  necessity  of  having  to 
cart  away  any  lime,  has  a  tendency  to  run  an  insuf- 
ficient quantity  of  lime.  The  result  of  this  is  that  he, 
commencing  at  the  top,  the  usually  less  important  part 
of  the  building,  has  used  up  his  lime  by  the  time  he 
has  reached  the  principal  rooms  on  the  ground  floor, 
and  has  to  have  recourse  to  possibly  insufficiently  sea- 
soned lime,  with  an  unfortunate  effect  on  the  work,  as 
stated  above. 

SAND. 

The  Functions  of  Sand  as  used  in  plaster  are  (1)  the 
production  of  regular  shrinkage  and  the  prevention  of 
excessive  shrinkage,  otherwise  cracking  is  the  result  5 
(2)  to  form  channels  for  the  crystallizatioii. 


MATERIALS 


Sand  should  be  clean,  sharp,  and  hard.  The  size  of 
the  grains  does  not  influence  the  strength  of  the  mortar, 
but,  of  course,  the  finer  the  plaster  is  required  to  be 
the  finer  must  the  sand  be.  Fine  sand  is  best  for  hy- 
draulic lime  and  coarse  for  fat  limes,  coarse  stuff  and 
Portland  cement  for  floating.  Uniformity  of  size  is 
not  desirable. 

The  Proportiofi  of  Sand  to  Lime  will  vary  consider- 
ably,  according  to  circumstances,  and  is  difficult  to  de- 
termine. One  part  of  lime  to  two  parts  of  sand  is  a 
usual  mixture. 

Sand  is  Cheaper  than  Lime,  and  it  must  be  remem- 
bered that  this  is  an  inducement  to  use  too  large  a  pro- 
portion of  sand  in  order  to  cheapen  the  plaster. 

Sand  is  Obtained  from  rivers,  pits,  or  the  sea.  Sea 
sand,  or  that  from  tidal  rivers,  should  be  avoided,  as 
the  salt  never  dries,  and  will  come  out  on  the  surface 
sooner  or  later,  discoloring  the  wall  papers,  paint,  etc., 
and  keeping  the  walls  damp. 

River  Sand  is  often  used,  but  it  is  not  to  be  recom- 
mended, because  the  sharpness  of  the  grains  is  worn 
off  by  the  action  of  the  running  water.  It  is  easily 
obtained,  however,  and  the  light  color  of  much  river 
sand  causes  it  to  be  used  in  internal  work  with  the 
v»-hite  cements. 

Pit  Sand  is  the  best.  It  sometimes  contains  loam  or 
clay,  which  should  be  carefully  washed  out. 

All  Sand  for  High-Class  Plastering  is  best  washed. 

HAIR. 

Hair  is  used  in  plaster  in  order  to  bind  it  together. 

Good  Hair  should  be  long,  curled,  strong,  and  clean. 
Ox  or  cow  hair  is  most  generally  used,  and  there  are 
three  qualities. 


30 


CEMENTS  AND  CONCRETES 


It  Should  Be  Well  Separated  before  being  mixed 
Avith  the  plaster,  and  care  should  be  taken  in  the  mix- 
ing that  the  hairs  are  not  broken. 

CEMENTS. 

Portland  Cement,  with  a  large  proportion  of  sand, 
as  much  as  90  per  cent.,  is  useful  for  internal  work; 
it  may  be  used  as  a  backing  for  a  thin  floating  of  the 
white  cements. 

The  Heavier  and  Slower  in  Setting  cements  are  gen- 
erally the  stronger;  but  in  such  plasterer's  work  as 
rendering  walls  the  quicker  setting  cements  may  be  used 
without  disadvantage. 

Roman  Cement  is  a  natural"  cement.  It  is  liable 
to  effloresce  on  the  surface,  but  is  useful  where  quick 
setting  with  expansion  is  required,  as  in  underpinning 
or  repairs,  without  any  great  ultimate  strength. 

Other  ^'Natural  Cements''  very  similar  to  Roman 
are  Medina,  Rosendale,  Windsor,  etc.,  and  are  also  use- 
ful where  quick  setting  is  required. 

The  Use  of  the  Natural  Cements  is  much  restricted 
at  the  present  time  as  compared  with  artificial  cements, 
such  as  Portland. 

Parian  Cement  is  valuable  for  internal  work,  by  rea- 
son of  its  hardness,  nonporosity,  and  quick  setting 
properties.  It  is  hence  useful  in  cases  where  the  walls, 
mouldings,  etc.,  have  to  stand  rough  usage.  It  is  also 
washable.  This  cement  will  not  admit  of  being  re- 
worked. 

Eeene's  Cement  is  one  of  the  most  useful  of  the 
artificial  cements.  It  is  harder  than  the  other  kinds 
made  from  plaster  of  Paris,  and  is  much  used  for  pilas- 
ters, columns,  etc.^  as  it  sets  quickly  and  can  be  pol- 
ished, and  takes  paint  excelleiitly. 


MATERIALS 


31 


Martin's  Cement  is  much  the  same  as  Keene's,  and 
used  principally  for  dadoes,  etc.  In  proportion  to  its 
bulk  it  covers  a  large  proportion  of  surface.  It  can 
be  painted,  etc.,  as  Keene's. 

Robinson's  Cement  has  many  advantages,  among 
which  are  its  fire-resisting  qualities  and  suitability  for 
use  on  concrete.  It  is  also  cheaper  than  other  like 
cements. 

Adamant  is  another  white  cement,  which  is  useful  for 
work  where  hardness,  facility  of  application,  quick  dry- 
ing, and  a  fine  surface  are  required. 

The  Above  Cements  have  plaster  of  Paris  (calcined 
gypsum)  for  their  base,  and  are  only  adapted  for  in- 
ternal uses,  to  which  they  are  eminently  suited.  They 
can  all  be  brought  to  a  good  surface,  and  can  be  painted 
almost  at  once. 

Selenitic  Cement  is  based  on  the  property  which  sul- 
phate of  lime  as  plaster  of  Paris,  when  added  to  lime 
possessing  hydraulic  properties,  has  of  causing  its  more 
rapid  setting.  It  also  increases  the  proportion  of  sand 
which  it  will  bear.  It  is  useful  in  plastering  as  a  back- 
ing for  the  white  cements,  such  as  Parian. 

PLASTER  OF  PARIS. 

Plaster  of  Paris  is  made  by  the  gentle  calcination  of 
gypsum,  previously  ground.  It  is  known  in  the  plas- 
tering trade  as  plaster. 

The  Principal  Use  of  Plaster  of  Paris  is  in  mixing 
with  ordinary  putty  in  order  to  produce  greater  rapid- 
ity in  setting,  but  the  fast  setting  plasters  of  Paris  are 
not,  of  course,  the  best  for  working  with,  nor  do  they 
become  as  hard  as  the  slower  setting. 

The  Proportion  of  Plaster  of  Paris  to  ordinary  lime 
putty  varies  greatly  from  about  1  in  4  to  1  in  20,  de- 


32  CEMENTS  AND  CONCRETES 


pending  on  circumstances,  such  as  the  state  of  the 
weather,  the  speed  with  which  the  work  has  to  be  fin- 
ished, etc.  It  is  also  used  largely  for  cast  ornaments, 
in  cornices,  etc.,  and,  by  reason  of  its  quick  setting/and 
expansion  when  setting,  for  stopping  holes,  etc. 

LATHS. 

Pine,  Cedar  and  Metal  are  used  for  laths  for  mod- 
ern work;  only  the  best  quality  should  be  used. 

Oak  Laths  and  Cypress  formerly  used,  are  very  liable 
to  warp. 

The  Defects  to  Be  Avoided  in  Laths  are  sap,  knots, 
crookedness,  and  undue  smoothness.  The  sap  decays; 
the  knots  weaken  the  laths;  the  crookedness  interferes 
with  the  even  laying  on  of  the  stuff;  and  the  undue 
smoothness  does  not  give  sufficient  hold  for  the  plaster 
on  the  lath. 

Riven  Laths,  split  from  the  log  along  its  fibres,  are 
stronger  than  sawn  laths,  as  in  the  latter  process  the 
fibres  of  the  wood  are  often  cut  through. 

Laths  May  Be  Obtained  in  Three  Sizes,  namely: 
'^Single''  (average  1-8  in.  to  3-16  in.  thick),  ^^lath  and 
half"  (average  in.  thick)  and  ^^double''  (%  in.  to 
%  in.  thick). 

The  Thicker  Laths  should  be  used  in  the  ceilings,  be- 
cause of  the  strain  upon  them,  and  the  thinner  in  ver- 
tical partitions,  etc.,  where  there  is  but  little  strain. 
Where  walls  and  partitions  have  to  stand  rongli  usage 
the  thicker  laths  are  necessary. 

Laths  Are  Usually  Spaced  with  about  %  in.  between 
them  for  key. 

A  Bunch  of  Laths  usually  contains  a  hundred  pieces, 
and  such  a  bunch  nailed,  with  butt  joints,  cover  about 


MATERIALS 


33 


4^  yds.  super.,  and  requires  about  500  nails  if  nailed 
to  joists  1  ft.  from  center  to  center. 

The  Lengths  of  Laths  vary  from  3  ft.  to  4  ft.,  the 
latter  the  usual  length. 

Laths  Are  Best  Nailed  so  as  to  Break  Joint  entirely, 
as  for  various  reasons  there  is  a  tendency  to  crack  along 
the  line  of  the  joints  if  nailed  with  the  butt  ends  in  a 
row.  This  may  be  obviated  by  using  3  ft.  and  4  ft.  laths 
together.  Ceilings  are  much  stronger  if  so  nailed. 
Laths,  however,  are  usually  nailed  in  bays,  about  4  ft. 
or  5  ft.  deep. 

Every  Lath  should  be  nailed  at  each  end,  and  wher- 
ever it  crosses  a  joist  or  stud. 

Lap  Joints  at  the  end  of  laths,  which  are  often  made 
in  order  to  save  nails,  should  not  be  allowed  as  this 
leaves  only  i/4  i^-  for  the  thickness  of  plaster.  Butt 
joints  should  always  be  made. 

Joists  J  etc,  J  which  are  thicker  than  2  in.  should  have 
small  fillets  nailed  on  their  under  side  or  be  counter- 
lathed,  so  that  the  timber  surface  of  attachment  be  re- 
duced to  a  minimum  and  the  key  be  not  interfered  with. 

Walls  which  are  liable  to  damp  are  sometimes  bat- 
tened or  strapped. 

Metal  Lathing  is  now  extensively  used  for  its  fire- 
proof qualities  and  freedom  from  rot  or  harboring  of 
vermin. 

Lathing  Nails  are  usually  of  iron — galvanized,  cut, 
wire,  or  cast;  where  oak  laths  are  used,  the  nails 
should  be  galvanized  or  wrought.  Galvanized  nails 
should  also  be  used  with  white  cement  work.  Zinc 
nails,  which  are  expensive,  are  used  in  very  good  work, 
because  of  the  possibility  of  the  discoloration  of  the 
plaster  by  the  rusting  of  iron  nails. 


34  CEMENTS  AND  CONCRETES 


The  Length  of  Lathing  nails  depends  on  the  thick- 
ness of  the  laths,  %  in.  long  nails  being  used  for  shin- 
gle laths,  1  in.  nails  for  lath  and  half  iaths,  and  li/4  i^- 
nails  for  double  laths. 

MEMORANDA. 

One  Yard  Rendering  requires  1-3  cu.  ft.  lime,  cu. 
ft.  sand,  oz.  hair,  and  1%  gal.  water.  One  yard 
render  and  set  requires  %  cu.  ft.  lime,  %  cu.  ft.  sand, 
3  oz.  hair,  and  2  gal.  water. 

One  yard  render,  2  coats  and  set,  requires  3-5  cu.  ft. 
lime,  2-3  cu.  ft.  sand,  3  oz.  hair,  and  2^/2  gal.  water. 

One  yard  render  and  float  requires  1/2  cu.  ft.  lime, 
%  cu.  ft.  sand,  2^/2  oz.  hair,  and  2^2  g^l-  water. 

One  yard  render,  float  and  set,  requires  3-5  cu.  ft. 
lime,  %  ft.  sand,  3%  oz.  hair,  and  2%  gal.  water. 

Two  bushels  of  gray  lime,  or  3  of  blue  lias  lime,  or 
3  of  Roman  cement,  or  2  of  Portland  cement,  or  14  lbs. 
plaster  of  Paris,  equal  one  bag. 

1  lb.  hair  is  allowed  to  2  cu.  ft.  of  coarse  stuff  for 
good  work,  and  3  cu.  ft.  for  common  work. 

100  yd.  super,  of  lime  whiting,  if  once  done  requires 
1^  cu.  ft.  of  lime;  and  if  twice  done,  2  cu.  ft.  of  limCo 


WORKMANSHIP. 


EXTERNAL  WORK. 

Portland  Cement  is  unquestionably  the  best  material 
for  external  plastering.  For  weather  resisting  proper- 
ties, strength,  and  capacity  for  moulding  and  painting, 
it  is  unequalled. 

The  Cement  for  Rendering  requires  to  be  mixed  with 
sand  in  the  proportion  of  about  1  of  cement  to  4  of 
sand,  but  for  projecting  cornices,  etc.,  the  proportion 
of  sand  should  be  only  about  half  this,  as,  of  course,  the 
addition  of  sand  decreases  the  adhesive  power  of  the 
cement.  The  fining  coat  is  mixed  in  the  proportions  of 
about  2  to  1. 

External  Facades  in  Portland  Cement  are  usually 
laid  in  two  coats ;  the  first  coat,  known  as  the  rendering 
or  floating  coat,  is  worked  to  screeds,  and  is  from  i/^ 
in.  to  %  in.  thick.  This  coat  must  be  carefully  cleared 
and  well  wetted  for  the  second  coat,  which  is  known 
a^  the  finishing  or  fining  coat,  which  is  about  3-16  in. 
thick,  and  is  worked  with  a  hand  float. 

The  Key  for  External  Plastering  on  brick  work  may 
be  obtained  either  by  building  the  walls  roughly  with 
the  mortar  projecting  or  by  raking  the  joints  at  least 
%  in.    Stone  work  should  be  hacked. 

The  Surface  Must  Be  Well  Wetted,  or  the  wall  will 
absorb  the  water  from  the  rendering  coat. 

There  is  a  Tendency  to  Mix  Fat  Lime  with  Portland 
cement  in  order  to  make  it  work  more  freely,  but  this 
should  not  be  allowed. 

35 


36 


CEMENTS  AND  CONCRETES 


Stucco  is  the  term  which  is  loosely  applied  to  all 
kinds  of  external  plastering,  whether  of  lime  or  cement. 
An  enormous  amount  of  stucco"  was  done  at  the  end 
of  the  eighteenth  century  and  the  beginning  of  the 
nineteenth,  but  is  now  out  of  fashion,  except  for  coun- 
try and  suburban  residences.  The  term  is  also  applied 
to  some  forms  of  internal  plastering.  The  principal 
varieties  of  stucco  are  common,  rough,  bastard,  and 
trowelled,  but  cement  has  largely  superseded  them. 

Common  Stucco  was  principally  employed  for  ex- 
terior work,  and  was  composed  of  1  part  hydraulic  lime 
and  3  parts  sand.  The  surface  of  the  wall  should  be 
rough  and  wet  as  for  Portland  cement  rendering. 

Rough  Stucco  was  used  on  a  floated  ground  in  po- 
sitions where  it  was  desired  to  imitate  stone.  It  was 
worked  with  a  hand  float  covered  with  a  material  such 
as  rough  cloth,  in  order  to  raise  the  sand  and  produce 
a  stone-like  appearance.  Cement  is  now  used  for  the 
same  purpose. 

Bastard  Stucco  and  Trowelled  Stucco  were  chiefly 
adapted  for  painted  internal  work,  and  each  is  laid  on 
the  second  coat  as  a  finish;  the  first  and  second  coats 
being  as  for  ordinary  three-coat  work. 

Troivelled  Stucco  consists  of  1  part  sand  to  2  parts 
fine  stuff.  It  is  worked  with  the  hand  float  till  a  very 
fine  smooth  surface  is  produced. 

Bastard  Stucco  contains  a  little  hair  and  has  not  so 
much  labor  expended  upon  it. 

Sgraffito  is  the  name  given  to  ornament  which  is 
scratched  on  plaster  work.  Patterns  may  be  obtained 
by  laying  differently  colored  coats  (usually  two  or 
three)  on  ordinary  roughened  Portland  cement  ren- 
dering, and  removing  portions  of  each  coat  in  the  form 
of  a  pattern. 


WORKMANSHIP 


37 


The  Design  for  the  Sgraffito  is  applied  in  a  cartoon 
and  pricked  and  pounced  on  the  work  in  the  usual  way. 
If  more  colors  are  required  than  the  coats  provide,  the 
background  may  be  washed  and  a  combination  of 
sgraflSto  and  fresco  used.  The  cutting  should  be  deep 
enough  to  give  a  sharp  appearance,  but  not  too  deep 
tc  hold  dirt  and  wet. 

Rough  Cast,  also  known  as  pebble  dashing,  is  the 
coarsest  kind  of  external  plastering.  It  is  very  durable 
if  properly  mixed.  Its  use  in  this  country  dates  back 
to  very  early  times.  The  wall  is  first  plastered,  and 
gravel,  shingle,  or  other  materials  such  as  spar,  broken 
bricks  and  glass  bottles,  broken  pottery,  etc.,  are  thrown 
or  dashed  at  it  while  it  is  soft.  If  the  gravel  is  mixed 
and  laid  with  the  plaster  there  is  a  tendency  in  laying 
for  it  to  tear  the  plaster  away  from  the  wall,  and  as 
the  gravel  is  covered  with  plaster  its  appearance  is  not 
so  good.  The  lime  for  rough  cast  should  be  weather 
resisting,  and  is  generally  used  hot. 

Depeter  is  a  form  of  rough  cast  on  which  the  gravel 
is  pressed  in  by  the  hand.  Ornamental  patterns  in 
color  may  be  worked  in  it.  Effective  but  simple  deco- 
rations for  external  plaster  may  be  made  in  various 
ways.  Patterns,  such  as  sunflowers,  etc.,  may  be  in- 
cised in  it,  and  a  very  effective  decoration  has  been 
obtained  by  merely  tapping  the  plaster  with  a  scratch 
six  or  seven  times  alternately  in  a  diaper  pattern.  In 
half-timber  work  the  plaster  is  much  more  pleasing  if 
carefully  laid  with  a  carelessly  unlevel  surface,  and,  of 
course,  set  back  from  the  timber  face  about  %  in. 

INTERNAL  WORK. 

Lime  Plastering  is  compounded  of  lime,  sand,  hair, 
and  water.    The  proportions  of  these  materials  vary 


38  CEMENTS  AND  CONCRETES 


according  to  their  nature  and  the  position  of  the  plas- 
ter. For  successful  work  good  materials  and  skillful 
mixing  are  essential.  It  is  applied  in  one,  two,  or  three 
coats,  and  by  the  number  of  these  the  plaster  is  named. 

The  Thinner  the  Coats  of  plaster  are  the  better,  as 
the  plaster  has  a  better  chance  of  drying  and  harden- 
ing. 

One-Goat  Work,  necessarily  the  commonest  and 
cheapest,  is  limited  to  very  inferior  buildings,  such  as 
outhouses  and  places  where  it  will  not  be  seen,  as  be- 
hind skirtings.  One-coat  work  on  laths  is  specified  as 
^^lath  and  lay, ''-or  ^^lath  and  plaster,"  and  on  wails 
simply  as  ^ ^render." 

TwO'Coat  Work  is  that  usually  employed  in  inferior 
work,  such  as  factories,  warehouses,  etc.,  but  it  is  also 
used  for  the  least  important  rooms  in  better  class  build- 
ings. Common  setting  for  walls  and  ceilings  is  gener- 
ally used  for  this  class  of  work.  Two-coat  work  on 
laths  is  specified  as  ^^lath,  lay,  and  set,"  or  '4ath,  plas- 
ter, and  set,"  and  on  walls  as    render,  and  set." 

Three-Coat  Work  is  that  used  in  all  good  buildings, 
and  forms  a  most  satisfactory  wall  finish,  when  well 
done.  Three-coat  work  on  laths  is  specified  as  ^4ath, 
lay,  float,  and  set,"  or  ''lath,  plaster,  float,  and  set," 
and  on  walls  as  ''render,  float,  and  set." 

The  Processes  in  Plastering  ordinary  three-coat  work 
are  as  follows: 

For  the  First  Coat  a  layer  of  well-haired  coarse  stuff 
known  as  pricking-up  is  laid  to  a  thickness  of  about 
%  in.  This  should  be  laid  diagonally  and  w^ith  each 
trowelful  overlapping.  If  on  laths  it  should  be  soft 
enough  to  be  well  worked  through  them  to  form  a  key. 
'The  surface  is  then  scratched  with  a  lath  to  form  a 
key  for  the  next  coat  in  lines  abo^it  4  in.  apart.    It  is 


WORKMANSHIP 


39 


ready  for  the  second  coat  when  too  hard  to  receive  an 
impression  from  ordinary  pressure. 

The  Coarse  Stuff  used  in  the  first  coat  is  mortar  com- 
posed of  sand  and  lime,  usually  in  the  proportions  of  2 
to  1,  with  plenty  of  hair,  so  that  when  a  trowelful  is 
taken  up  it  holds  well  together  and  does  not  drop. 

The  Second  Coat  known  as  floating,  is  next  laid. 
Four  processes  are  involved  in  laying  the  second  coat, 
namely:  Running  the  screeds,  filling  in  the  spaces, 
scouring  and  keying  the  surface.  The  scouring  is  done 
with  a  hand  float,  the  surface  being  sprinkled  by  a 
brush  during  the  process.  The  keying  consists  in  lining 
the  scoured  surface  with  a  broom  or  nail  float  to  form 
an  adhesive  surface  for  the  finishing  coat. 

The  Floating  is  of  finer  quality  than  the  coarse  stuff, 
it  does  not  contain  as  much  hair,  and  is  used  in  a  softer 
state. 

The  Third  Coat  is  the  finishing  coat,  and  is  known 
as  the  setting  coat.  Great  care  must  be  taken  in  laying 
this  coat  in  order  to  obtain  uniformity  of  surface,  color, 
smoothness,  and  hardness.  The  second  coat  should  be 
uniformly  keyed,  clean  and  damp  before  the  third  is 
laid.  The  processes  involved  are  laying,  scouring,  trow- 
elling, and  brushing. 

Fine  Stuff,  which  should  be  used  for  the  finishing 
coat  if  the  walls  are  to  be  papered,  consists  of  pure 
lime,  slaked  and  then  saturated  till  semi-fluid,  and  al- 
lowed to  stand  till  the  water  has  evaporated  and  it 
forms  a  paste.  It  may  then  be  thoroughly  mixed  with 
fine  sand  in  the  proportion  of  3  parts  of  sand  to  1  part 
of  fine  stuff. 

Plasterers^  Putty  is  much  like  fine  stuff,  but  is  care- 
fully sieved. 


40  CEMENTS  AND  CONCRETES 


Gauged  Stuff  is  plasterers'  putty  and  plaster  of 
Paris  in  the  proportion  of  three  or  four  to  one.  If  too 
much  plaster  is  used  it  cracks  in  setting.  It  is  largely 
used  in  cornices,  and  also  where  the  second  coat  is  not 
allowed  time  to  dry,  and  the  work  has  to  be  done  in  a 
hurry.  As  it  sets  rapidly,  it  must  be  mixed  in  small 
quantities. 

The  White  Cements  (such  as  Parian,  etc.),  of  which 
plaster  of  Paris  is  the  base^  are  usually  laid  in  two 
coats;  the  first,  of  cement  and  sand,  is  about  I/2  in.  to 
34  in.  thick,  and  the  second  of  the  cement  neat. 

Cracks  in  Plaster  Work  are  caused,  apart  from  the 
natural  settlement  of  the  building  and  the  use  of  in- 
ferior materials  and  workmanship,  by  the  too  fast  dry- 
ing of  the  work,  the  laying  of  the  plaster  on  walk  of 
too  great  suction,  by  laying  one  coat  on  another  before 
the  lower  one  has  properly  set,  and  by  the  use  of  too 
little  sand. 

Joist  Lines  on  Ceilings  are  very  unsightly,  and  are 
caused  by  the  filtration  of  dust  through  the  intervening 
spaces.  They  may  be  prevented  by  using  a  good  thick- 
ness of  plaster,  and  working  it  well,  that  it  may  be  hard 
and  nonabsorbent  and  as  the  dust  comiCS  from  the  top 
and  filters  through,  by  protecting  the  upper  side  of  the 
plaster. 

Pugging  consists  in  laying  a  quantity  of  plaster  be- 
tween the  joists  of  a  floor  or  between  the  studding  of 
a  partition  for  the  purpose  of  preventing  the  passage 
of  sounds  or  odors.  In  the  first  case,  which  is  the  more 
common,  the  plaster  is  laid  on  thin,  rough  boards  fixed 
to  battons  on  the  sides  of  the  joists;  in  the  second  case, 
which  is  called  '  ^  counterlathing "  in  some  parts  of  the 
country,  by  plastering  on  laths  nailed  between  the  par- 
tition studs. 


WORKMANSHIP 


41 


Pugging  Should  Not  Be  Used  Too  Wet,  There  are 
three  objections  to  this — the  first  that  it  takes  a  very 
long  and  inconvenient  time  in  drying;  and  secondly, 
that  the  water  is  liable  to  be  absorbed  by  the  wood, 
and  to  cause  it  to  rot;  and  thirdly,  it  is  liable  to  crack 
in  the  drying.  For  this  last  reason  it  should  always  be 
laid  in  two  coats. 

The  Battons  should  all  be  nailed  at  an  equal  depth 
from  the  tops  of  the  joists,  and  the  plaster  should  be 
of  an  equal  thickness  throughout,  which  is  obtained  by 
drawing  a  trammel  along  the  joists. 

Mineral  Wool  is  far  more  sanitary  than  ordinary 
pugging,  has  considerable  sound  and  fire  resisting  qual- 
ities, it  does  not  absorb  moisture  and  so  rot  the  laths 
and  timbers,  is  a  preventive  of  vermin,  and  is  light  in 
weight. 

Lime  Whiting  or  Whitewash  which  is  lime  dissolved 
in  water,  is  a  useful  and  sanitary  covering  for  the 
walls  of  cellars  and  outhouses. 

If  Lime-Whited  Walls  Have  to  Be  Plastered,  the  wall 
should  be  first  carefully  picked,  as  if  the  lime  is  left  on, 
the  plaster  is  liable  to  scale. 

Fibrous  Plaster  is  composed  of  plaster,  canvas,  wood, 
etc.    It  is  light  and  dry  and  can  be  quickly  fixed. 

Ornamental  Plaster  ceilings  may  be  either  modelled 
throughout  in  situ,  or  cast  in  pieces,  or  formed  by  work- 
ing the  ornament  on  a  previously  formed  flat  ceiling. 
The  first  method  is  the  more  costly,  but  more  feeling 
is  thereby  obtained. 


1 


SPECIFICATION  CLAUSES. 

MATERIALS. 

1.  The  sand  for  plastering  is  to  be  fresh-water  river, 
or  pit  sand,  and  free  from  earthy,  loamy,  or  saline 
material,  to  be  well  screened,  and  to  be  washed  if  re- 
quired. 

2.  The  laths  to  be  straight-riven  or  saron  pine  of  the 
strength  known  as  lath  and  half,  well  nailed  with  lin. 
oxidized  lath  nails,  properly  spaced  for  key,  and  with 
butt-headed  joints,  double  nailed,  and  breaking  joint 
in  3  ft.  widths. 

The  lathing  to  be    Expanded  metal,''  No.  —  gauge. 

3.  The  lime  for  coarse  stuff  to  be  approved  well- 
burnt  grey-stone  lime,  to  be  run  at  least  one  month 
before  being  required  for  use,  to  be  kept  clean,  and 
well  mixed  as  required  with  two  parts  sand  and  one 
part  lime. 

4.  The  coarse  stuff  for  ceilings,  lath  partitions,  and 
elsewhere  where  directed  to  have  1  lb.  of  good,  long 
curled  cowhair,  free  from  grease,  leading,  or  other  im- 
purities, well  beaten  in,  and  incorporated  with  every 
3  cu.  ft.  of  coarse  stuff. 

5.  Approved  lime,  free  from  lumps,  flares,  or  core, 
is  to  be  used  for  setting,  putty,  etc.,  and  is  to  be  run 
at  least  one  month  before  being  required  for  use. 

6.  The  Portland  cement  is  to  be  of  the  best  quality 
and  description  for  plastering  purposes,  from  an  ap- 
proved manufacturer,  and  must  on  no  account  be  used 
fresh,  but  be  spread  out  to  cool  for  at  least  ....  weeks 
in  a  dry  shed  or  room. 

42 


SPECIFICATION  CLAUSES  43 


All  suitable  cement  and  all  other  materials  required 
in  plastering  are  to  be  of  the  best  of  their  respective 
kinds  and  descriptions. 

7.  Provide  all  plasterers'  plant,  necessary  scaffold- 
ings, tools,  moulds,  running  rules,  straight  edges,  tem- 
plates, etc.,  of  every  kind  and  description  necessary  for 
the  proper  execution  of  the  work. 

WORKMANSHIP. 

8.  Lath,  plaster,  float,  and  set  all  wood  joist  ceil- 
ings, soffits,  and  stud  partitions,  and  finish  partitions  to 
line  in  trowelled  stucco. 

The  concrete  ceilings  and  soffits  are  to  be  well  hacked 
for  key  and  floated  and  set  in  gauged  stuff,  and  the 
concrete  partitions  are  to  be  floated  and  set. 

Do  all  dubbing  out  where  required  to  concrete  ceil- 
ings, soffits,  and  partitions  in  gauged  stuff. 

The  concrete  soffits  of  strong  rooms  to  be  finished 
with  one  coat  of  putty  gauged  with  plaster  only. 

9.  Cover  all  chases  containing  pipes,  etc.,  with  heavy 
wire  lathing  suitable  for  plastering  on,  securing  the 
same  in  a  thorough  manner.  The  wire  lathing  to  be 
wetted  in  lime  water  before  being  put  on. 

10.  Render,  float,  and  set  all  walls  where  not  other- 
Mdse  described.    The  walls  to  ......  to  be  finished  in 

trowelled  stucco. 

11.  All  cornices  and  moulded  work  throughout  to 
be  run  clean  and  accurately  to  the  sections  given. 

All  mitres  and  returns  to  be  truly  worked,  and  all 
enrichments  and  modelling  to  be  to  architect's  ap- 
proval, and  strictly  in  accordance  with  the  models  and 
instructions  given. 

Run  moulded  plaster  cornices  ....  girt  to  ....  rooms. 


44  CEMENTS  AND  CONCRETES 


with  all  mitres,  returned,  stopped,  and  mitred  ends, 
etc.,  as  required. 

The  cornices  to  ....  are  to  be  run  in  fibrous  plas- 
ter, fitted  and  fixed  with  proper  oxidized  nails,  and 
made  good  to. 

12.  All  narrow  reveals,  splays,  and  returns  to  be 
finished  in  suitable  cement  on  a  Portland  cement  back- 
ing. 

Eun  strong  cement  angles  and  arrises  on  Portland 
cement  backing  to  all  projecting  angles  except  the  fol- 
lowing, which  are  to  be  moulded,  viz. :  

Run  rounded  angles  to  of  3  in.  girt  in  strong 

cement  as  before. 

Run  avolo  moulded  angles  3  in.  girt  with  2  in.  wings 
to  ....  opening,  finished  with  moulded  stops  and  short 
lengths  of  angle  and  arris  to  detail,  all  in  best  cement. 

All  exposed  surfaces  of  concrete  lintels  and  girder 
casings  are  to  be  finished  in  white  cement  internally 
and  Portland  cement  externally,  kept  flush  with  faces 
of  brickwork;  all  with  arrises  and  angles  excepting 
those  otherwise  described. 

13.  Run  Portland  cement  flush  skirting  9  in.  high 
to  basement,  where  plastered,  with  flush  head  to  top  and 
trowelled  face. 

The  skirting  to  to  be  12  in.  high  and  1  in. 

projection,  sunk  and  twice  moulded  in  white  on  Port- 
land cement  backing. 

Float  off  the  concrete  floors  of  ....  in  Portland  ce- 
ment to  the  required  level  to  receive  mosaic  and  the 
pavings. 

14.  Run  all  necessary  quirks,  spla>s,  arrises,  etc., 
and  make  good  to  all  mantelpieces;  cut  away  for  and 
make  good  after  all  other  trades^  and  cut  out  and  make 


SPECIFICATION  CLAUSES 


good  all  cracks,  blisters,  and  other  defects,  and  leave 
plaster  work  perfect  at  completion. 

15.  Ding"  walls  where  shown  on  plans  with  a  coat  of 
Portland  cement  1  part,  sand  2  parts,  pea-grit  1  part, 
and  ground  chalk  1  part.  Finish  walls  where  shown 
with  a  rough  coat  of  Portland  cement  1  part  and  sand 
3  parts,  and  rough  cast  with  fine  pea-grit. 

16.  Stop  and  twice  lime  white  soffits  and  walls  of  .  . 

17.  Twice  distemper  white  all  ceilings,  soffits,  and 
cornices,  and  twice  distemper  to  approved  tints  the 
walls  of  all  rooms. 


PEEPARATION  OF  BILL  OF  QUANTITIES. 


MATERIALS. 

Materials  and  Plant,  etc. — 1  to  7.  These  items  ap- 
pear in  the  heading  under  Specification  clauses. 

WORKMANSHIP. 

Ceilings,  Partitions,  and  Walls. — 8  and  10.  These 
are  all  billed  at  per  yd.  super,  including  lathing  where 
required,  also  hacking  concrete  and  any  dubbing  in  the 
latter,  stating  the  thickness.  Keep  all  plaster  work 
less  than  12  in.  wide  separate  in    narrow  widths.'' 

Wirelathing. — 9.  These  being  narrow,  it  is  advisable 
to  measure  them  at  per  ft.  run,  stating  the  width. 

Cornices. — 11.  Cornices  and  mouldings  under  12  in. 
girt  are  measured  at  per  ft.  run  and  those  over  this 
girt  at  per  ft.  super,  number  all  mitres,  stoppings,  etc.  ; 
those  to  the  running  items  following  same,  and  those 
to  the  superficial  items  averaged  for  girt.  See  whether 
bracketing  is  required;  if  so,  take  the  girt  required  at 
per  ft.  super.,  numbering  angle  brackets  to  mitres  and 
returned  ends,  and  averaging  the  girt. 

Measure  the  walls  and  ceilings  less  by  the  height  and 
projection  of  the  cornice,  and  add  to  the  girt  of  the 
cornice  2  in.  (i.  e.,  1  in.  for  each  edge)  for  the  portion 
up  to  the  ceiling  and  walls. 

Enrichments  are  measured  at  per  ft.  run,  giving  the 
girt  and  description,  and  including  the  modelling.  If 

46 


BILL  OF  QUANTITIES 


47 


of  exceptional  character,  a  provision  for  modelling  is 
sometimes  inserted. 

Angles, — 12.  These  appear  in  bill  in  feet  run  with 
the  girt  of  moulding  or  bead  (if  any)  and  also  the 
widths  of  returns.  Number  the  stops,  mitres,  etc.,  al- 
lowing each  to  follow  the  item  to  which  they  apply. 

The  finishings  to  concrete  beams,  lintels,  etc.,  is  kept 
separate  as  in  narrow  widths  to  beams,  etc./'  and  all 
arrises,  etc.,  being  measured  at  per  ft.  run. 

Skirtings  or  Dadoes. — 13.  Describe  skirtings  or  dadoes 
giving  height  and  projection,  and  also  finish  at  top,  and 
measure  at  per  ft.  run,  numbering  all  mitres,  ends,  etc. 
Include  the  dubbing  with  the  item.  The  general  wall 
plastering  is  deducted  for  these. 

Floating  for  mosaic  and  tile  pavings  appears  in  the 
bill  in  yard  super. 

Quirks. — 14.  Labor  to  splays,  quirks,  arrises,  etc., 
are  measured  at  per  ft.  run. 

The  attendance  on  trades  is  frequently  measured  in 
detail,  as  ^'making  good  around  mantels"  or  gratings, 
etc. 

The  cutting-out  and  making  good  appears  at  the  end 
of  the  bill  in  the  form  here  given. 

Rough  Cast. — 15.    As  clauses  8  and  10. 

Lime  Whiting  and  Distempering. — 16  and  17.  These 
appear  in  the  bill  in  yd.  super.  In  the  case  of  distem- 
pering, if  the  colors  are  in  any  way  special  mention 
this,  and  also  if  in  dadoes  and  filling,  taking  the  di- 
viding line  in  feet  run. 

Distempering  on  cornices  is  usually  measured  in  ft. 
super.,  stating  the  number  of  tints,  and  if  lines  picked 
out  in  ft.  run ;  as  is  also  distempering  on  enrichments, 
taking  the  latter  as  ''extra  to,"  the  distempering  to 
cornices  being  measured  over  enrichments. 


48  CEMENTS  AND  CONCRETES 


LATHS  GENERALLY. 

General  opinion  is  undoubtedly  in  favor  of  split 
laths,  and  split  laths  are  sometimes  specified  by  archi- 
tects for  ceilings  and  partitions.  Sawn  laths,  unless 
cut  from  specially  selected  straight-grained  stuff,  would 
most  assuredly  have  weak  places  from  uneven  grain, 
and  in  order  to  avoid  this  weakness  the  sawn  laths 
would  have  to  be  made  thicker  than  split  laths,  and 
only  the  best  quality  should  be  used.  Oak  laths,  for- 
merly used,  are  very  liable  to  warp.  The  defects  that 
are  to  be  avoided  in  laths  are  sap,  knots,  crookedness, 
a.nd  undue  smoothness.  The  sap  decays;  the  knots 
weaken  the  laths ;  the  crookedness  interferes  with  the 
even  laying  on  of  the  stuff,  and  the  undue  smoothness 
does  not  give  sufficient  hold  for  the  plaster  on  the  lath. 
Riven  laths,  split  from  the  log  along  its  fibres,  are 
stronger  than  sawn  laths,  as  in  the  latter  process  the 
fibres  of  the  wood  are  often  cut  through.  Sawn  laths 
are,  however,  cheaper  than  riven  laths,  and  have  super- 
seded them,  which  is  not  desirable  in  good  work.  Thick 
laths,  because  of  the  strain  upon  them,  should  be  used 
in  the  ceilings,  and  the  thinner  laths  should  be  used  in 
vertical  partitions,  etc.,  where  the  strain  is  but  small. 
Some  walls  and  partitions  have  to  stand  rough  usage; 
in  such  cases  the  thicker  laths  are  necessary.  Laths  are 
usually  spaced  with  about  %  in.  between  them  for  key. 
A  bunch  of  laths  usually  contains  360  lin.  ft.  and  such 
a  bunch  nailed  with  butt  joints,  covers  about  4%  super, 
yd.,  and  requires  about  400  nails  if  the  laths  are  nailed 
to  joists  16  in.  from  center  to  center.  The  length  of 
laths  varies  from  3  ft.  to  4  ft.  Laths  are  best  nailed  so 
as  to  break  joint  entirely,  because,  for  various  reasons, 
there  is  a  tendency  to  crack  along  the  line  of  the  joints 


BILL  OF  QUANTITIES 


49 


if  the  laths  are  nailed  with  the  butt  ends  in  a  row.  This 
may  be  obviated  by  breaking  joints;  ceilings  are  much 
stronger  if  the  laths  are  nailed  in  this  way.  Laths, 
however,  are  usually  nailed  in  bays,  about  4  ft.  or  5  ft. 
deep.  Every  lath  should  be  nailed  at  each  end,  and  also 
at  the  place  where  the  lath  crosses  a  joist  or  stud.  Lap 
joints  at  the  end  of  laths,  which  are  often  made  in  or- 
der to  save  nails,  should  not  be  allowed,  as  this  leaves 
only  14  ill-  for  the  thickness  of  plaster.  Butt  joints 
should  always  be  made.  Joists,  etc.,  that  are  thicker 
than  two  in.,  should  have  small  fillets  nailed  to  the  un- 
der side,  or  be  counter  lathed,  so  that  the  timber  surface 
of  attachment  may  be  reduced  to  a  minimum  and  the 
key  not  interfered  with. 

Lathing  nails  are  usually  of  iron,  and  are  galvanized, 
cut,  wrought,  or  cast;  where  oak  laths  are  used,  the 
nails  should  be  oxidized  or  wrought.  Oxidized  nails 
should  also  be  used  with  white  cem^ent  work.  Zinc  nails, 
which  are  expensive,  are  used  in  very  good  work,  be- 
cause of  the  possibility  of  the  discoloration  of  the  plas- 
ter by  the  rusting  of  iron  nails.  The  length  of  lathing 
nails  depends  on  the  thickness  of  the  laths,  %  in.  nails 
being  used  for  single  laths,  and  1^/4  iii-  nails  for  double 
laths. 


TOOLS  AND  APPLIANCES  USED  BY  THE 
PLASTEREE. 


The  illustrations  shown  at  Pigs.  1  and  2  show  a  num- 
ber of  tools  and  appliances  made  use  of  by  the  plas- 
terer, and  others — special — will  be  shown  further  on, 
when  it  is  necessary  to  describe  and  illustrate  some 
speicial  process  or  method  of  working.  The  tools  the 
pla^erer  requires  are  many  and  varied,  and  may  be 
enumerated  about  as  follows:  They  consist  of  moulds 
for  running  cornices,  and  center  moulds,  which  may 
never  be  used  only  in  the  one  piece  of  work,  as  the  de- 
signs and  styles  of  cornices  and  centers  are  continually 
changing.  As  these  tools  do  not  cost  much,  however, 
the  changes  do  not  fall  heavily  on  the  workman;  but  it 
is  as  well,  whenever  it  can  be  done,  to  charge  each 
mould  against  its  own  particular  job  of  work.  A  good 
spade  and  shovel  will  be  absolutely  necessary  to  the 
plasterer's  outfit,  and  will  be  among  the  first  tools  he 
will  require.  These  should  be  light  and  strong,  and 
well  handled,  or  helved;  after  using  they  should  have 
all  the  lime  and  mortar  cleaned  off  them,  and  should 
be  placed  away  where  they  will  not  be  exposed  to  the 
weather. 

The  following  list  and  descriptions  of  tools  will  give 
a  new  beginner  an  idea  of  the  kind  and  character  of 
tools  he  will  be  likely  to  require  before  he  can  success- 
fully carry  on  the  plastering  business.  Most  of  these 
tools  will  be  illustrated  further  on: 

The  Hoes  and  Drags, — These  are  tools  so  well  known 
that  they  require  no  description  here.    They  are  used 

50 


52 


CEMENTS  AND  CONCRETES 


chiefly  for  mixing  hair  in  the  mortar,  and  for  loosening 
mortar  when  too  ''stiff/'  or  when  it  has  developed  a 
tendency  to  ''set."  They  are  also  used  for  preparing 
''putty"  and  fine  "stuff."    (See  Fig.  2.) 

The  Haivk,  which  is  a  square  board  about  thirteen 
inches  square,  with  a  short  handle  on  the  under  side. 
It  is  used  for  holding  stuff  while  the  operator  is  at 
work.  It  is  generally  made  of  pine  or  some  other  light 
wood;  it  is  made  thin  on  the  edges,  being  beveled  from 
the  center  on  the  under  side  to  each  of  the  four  edges; 
the  handle  should  be  about  six  inches  long,  and  one  and 
a  half  inches  in  diameter. 

The  Mortar-Board  is  a  board  similar  to  a  table  top^ 
and  is  about  forty  inches  square;  it  is  made  by  joint- 
ing two  or  more  boards  together,  which  are  secured  by 
two  battens,  and  screws  or  nails.  It  is  used  for  holding 
the  mortar  delivered  from  the  hod  direct  by  the  laborer. 

Trowels^  which  are  of  two  kinds :  the  ordinary  trowel, 
which  is  formed  of  light  sfeel  four  inches  wide  and 
about  twelve  inches  long;  this  is  the  laying  and  smooth- 
ing tool,  and  is  the  most  important  in  a  plasterer's  out- 
fit. The  other  is  termed  a  gauging  trowel,  and  is  used 
for  gauging  fine  stuff  for  courses,  etc. ;  it  varies  in  size 
from  three  to  seven  inches  in  length. 

Of  Floats^  which  are  used  for  floating,  there  are  three 
kinds,  viz. :  the  darby,  which  is  not  a  proper  float,  is 
single  or  double,  as  may  be  required;  the  single  being 
for  one  man  to  use,  the  double  for  two.  The  single  one 
should  be  four  feet  five  inches  long,  and  about  four 
inches  wide,  with  a  handle  near  one  end,  like  a  hawk 
handle,  and  a  cleat  near  the  other  end  running  length- 
wise of  the  blade;  the  long  darbys  have  a  hawk  handle 
on  each  end.  The  hard  float,  which  is  used  in  finishing, 
and  the  quick  float,  which  is  used  in  floating  angles. 


NO.  2. 


54  CEMENTS  AND  CONCRETES 


The  hard  float  is  made  of  good  pine,  and  has  a  semi- 
circular handle  on  the  back;  a  strip  of  hard  wood  is 
sometimes  dovetailed  into  the  blade,  and  the  handle  is 
screwed  fast  to  the  strip  previous  to  the  latter  being 
driven  in  the  dovetail;  this  is  a  good  way,  as  there  are 
no  nails  then  driven  through  the  blade,  which,  by  the 
rapid  wearing  of  the  latter,  would  soon  project  above 
the  blade  and  scratch  the  plaster  where  it  was  intended 
to  have  it  smooth.  The  quick  float  is  seldom  used  in 
this  country;  it  is  shaped  like  the  angle  it  is  intended 
to  work  down,  afid  is  a  trifle  handier  for  this  purpose 
than  the  ordinary  hard  float. 

Moulds, — These  are  used  for  running  stucco  cornices, 
and  are  infinite  in  shape  and  variety.  The  reverse  of 
the  contour  of  the  cornice  is  cut  out  of  sheet  copper  or 
iron,  and  is  firmly  attached  to  a  piece  of  wood  which 
is  also  cut  out  the  reverse  shape  of  the  intended  mould- 
ing. Their  uses  will  be  explained  under  the  head  of 
Operations.  Moulds  or  matrices  for  leaves,  flowers,  or 
other  ornaments  are  made  of  plaster  and  glue,  or  bees- 
wax; these  will  be  discussed  hereafter. 

Center-Moulds  are  made  on  the  same  principle  as  the 
reverse  moulds  for  linear  cornices,  with  an  arm  at- 
tached which  is  perforated  at  different  radii  to  suit  the 
diameter  of  center-piece.  Sometimes  the  moulds  for 
cornicing  are  so  formed,  by  placing  the  plates  at  an  an- 
gle of  fort3^-five  degrees,  that  they  will  finish  the  cor- 
nice right  into  the  angle  and  f orip  the  mitre ;  more  fre- 
quently, however,  the  mitres  are  finished  by  hand. 

The  Pointer  is  nearly  the  same  shape  as  a  bricklayer's 
trowel,  but  it  is  not  so  large,  being  only  about  four 
inches  long.  It  is  chiefly  used  for  small  jobbing,  or 
mending  broken  or  defective  vv^ork. 


TOOLS  AND  APPLIANCES 


55 


The  Paddle  is  simply  a  piece  of  pine  wood  less  than 
three  inches  wide  and  six  long,  by  one  thick ;  it  is  made 
wedge  shaped  on  one  end,  the  other  end  being  rounded 
off  for  a  handle.  Its  use  is  to  carry  stuff  into  angles 
when  finishing. 

Stopping  and  Picking-Oitt  Tools ^  or,  as  they  are  fre- 
quently called,  Mitering  Tools,  are  made  of  fine  steel 
plate,  seven  or  eight  inches  long,  and  of  various  widths 
and  shapes.  They  are  used  for  modeling,  and  for  fin- 
ishing mitres  and  returns  to  cornices  by  hand  where  the 
moulds  cannot  work. 

Mitering-Eod. — This  is  a  tool  one  foot  or  more  long, 
and  about  one-eighth  of  an  inch  thick,  and  three  inches 
wide;  the  longest  edge  is  sharp,  and  one  end  is  bev- 
elled off  to  about  thirty  degrees.  It  is  used  for  clean- 
ing out  quirks  in  mouldings,  angles,  and  cornices. 

The  Operator  also  requires  a  good  whitewashing 
brush,  with  a  short  handle.  The  best  should  be  ob- 
tained, as  it  will  prove  the  cheapest  in  the  end. 

A  Scratcher  is  generally  made  of  short  pieces  of  pine 
two  inches  wide  and  one  inch  thick;  three  or  four  of 
them  are  nailed  to  two  cleats,  and  are  placed  about  an 
inch  apart.  The  center  slat  should  be  about  eighteen 
inches  longer  than  the  others,  so  as  to  form  a  handle.' 
See  illustrations.  The  slats  on  the  opposite  end  to  the 
handle  should  be  cut  off  square  with  one  side  and  point- 
ed. Its  use  is  to  make  grooves,  or  bond  in  what  is  called 
the  scratch  coat.  When  completed  it  has  somewhat  the 
appearance  of  a  gridiron. 

Hod. — This  is  formed  by  two  boards,  eleven  and 
twelve  inches  wide,  respectively,  and  eighteen  inches 
long,  the  wide  board  being  nailed  on  the  edge  of  the 
narrow  one,  making  a  right-angled  trough;  one  end  is 
closed,  and  the  end  piece  is  rounded  over  the  top;  the 


56 


CEMENTS  AND  CONCRETES 


boards  forming  the  sides  are  rounded  at  the  opening. 
A  handle  about  four  feet  long  and  two  inches  in  diam- 
eter is  then  fastened  about  two  inches  forward  of  the 
middle  nearer  to  the  open  end,  and  a  piece  of  wood 
called  a  pad  is  fitted  with  a  groove  on  the  angle  just 
back  of  the  handle.  The  object  of  this  block  is  to  pre- 
vent the  arris  of  the  hod  from  chafing  the  shoulder  of 
the  laborer.  Much  controversy  has  taken  place  among 
workmen  at  various  times  regarding  the  exact  size  of 
hod,  but  this,  I  think,  should  be  governed  more  by  the 
strength  of  the  person  who  has  to  use  the  particular 
hod  than  by  any  fixed  rules.  Hods  for  carrying  mortar 
need  not  be  so  large  as  hods  intended  for  carrying 
bricks.    (See  No.  2,  Fig.  1.) 

Sieve. — This  is  used  for  straining  through  putty  for 
finishing;  it  requires  to  be  very  fine  for  the  purpose. 
Sometimes  a  hair  sieve  is  used,  but  they  are  not  last- 
ing, and  should  never  be  used  when  a  wire  sieve  is  ob- 
tainable. Sometimes  a  hair  sieve  may  prove  convenient 
where  dry  plaster  or  cements  have  to  be  run  through  a 
sieve  of  some  kind  before  it  can  be  used;  so,  on  the 
whole,  the  plasterer  who  desires  a  full  and  complete 
outfit,  should  provide  himself  with  one  good  hair  sieve, 
and  at  least  two  sieves  of  wire.    (See  Fig.  7,  No.  1.) 

Sand  Screens  are  usually  twenty-one  inches  wide  in- 
side by  about  six  feet  long.  On  small  work  they  are 
stood  up  at  an  angle  of  forty-five  or  more  degrees,  and 
the  sand  is  shovelled  against  them;  in  some  large  works 
the  screen  is  suspended,  and  one  man  shovels  in  the 
sand  and  a  second  one  swings  or  shakes  the  screen. 
These  screens,  to  be  lasting,  should  have  their  sides  and 
ends  made  of  sheet  iron,  and  the  bottom  should  be 
formed  with  parallel  rods  of  small  round  iron  having 
wires  running  across  them  at  regular  intervals.  These 


TOOLS  AND  APPLIANCES  57 


cross  wires  should  be  attached  to  the  iron  rods  so  as  to 
hold  them  in  place.  The  parallel  rods  may  be  placed 
at  such  distances  from  each  other  as  will  be  most  con- 
venient for  the  work  in  hand. 

Mo7^tar  Beds  are  made  of  rough  lumber  of  any  kind, 
and  should  be  built  partly  in  the  ground,  where  cir- 
cumstances will  permit.  They  require  to  be  strongly 
put  together,  as  they  have  considerable  weight  to  sus- 
tain. The  writer  has  seen  mortar  beds  built  up  with 
bricks  and  cement  where  large  works  have  been  under 
construction.  Sometimes,  master  workmen,  who  do  a 
large  business,  and  who  employ  a  great  number  of  men, 
keep  a  large  mortar  bed  or  two  in  the  rear  yard  of 
their  shop  and  tool  house,  in  which  they  keep  always 
on  hand  a  supply  of  ready-made  stuff,  which  enables 
them  to  do  small  jobs  or  repairs  at  a  moment's  notice. 

The  Slack  Box, — This  is  generally  made  of  boards, 
and  is  eight  or  nine  feet  long,  and  from  two  to  four 
feet  wide,  and  twelve  or  sixteen  inches  in  depth.  An 
opening  about  eight  inches  square  is  left  in  one  end, 
with  a  slide  door  attached,  so  that  it  can  be  opened  or 
closed  at  pleasure.  The  opening  should  be  covered  on 
the  inside  with  a  grating,  so  that  when  the  lime  is  run 
off  no  lumps  or  stones  will  get  through.  The  grating 
may  be  made  with  iron  rods,  or  may  be  formed  with 
wooden  laths  or  slats.  The  bottom  of  the  box  should 
be  made  as  close  and  tight  as  rough  boards  will  permit. 
(See  No.  1,  Fig.  11.) 

Lathing.i — It  frequently  happens  in  towns  and  coun- 
try places  that  the  plasterer  has  to  do  his  own  lathing^ 
or  at  least  have  it  done  under  his  own  supervision, 
therefore  it  will  be  necessary  to  have  something  to  say 
on  this  subject,  and  on  the  tools  employed  by  the  work- 
man whose  duty  it  is  to  prepare  the  walls  for  the  plas- 


58  CEMENTS  AND  CONCRETES 


terer.  These  tools  need  not  be  extravagant  ones  or 
many  in  number.    They  consist  of  the  following: 

Lather's  Hatchet. — ^This  is  a  small  hatchet  with  a 
blade  not  more  than  one  and  a  half  inches  wide,  and 
rather  larger  in  proportion  than  ordinary  hatchets. 
The  opposite  end  to  the  cutting  edge  is  a  hammer,  with 
which  the  lather  drives  the  nails.  Sometimes  the  face 
of  the  hammer  end  is  grooved,  which  makes  it  cling  to 
the  nails  if  the  latter  are  not  struck  fairly  on  the  head. 
An  expert  lather,  however,  will  prefer  a  flat  hammer 
face  for  driving  lath  nails.  The  cutting  edge  is  used 
for  nipping''  off  laths  when  they  are  too  long,  or 
Avhen  short  spaces  of  lathing  are  required  to  be  made. 
In  cutting  lath  with  the  hatchet,  the  workman  gives  the 
wood  a  short  sharp  blow  with  the  tool  at  the  point 
where  the  severance  is  required,  and  the  lath  is  in- 
variably cut  at  the  first  blow,  if  the  operator  is  an  ex- 
pert.   (See  0,  Fig.  2.) 

Nail  Pocket, — Perhaps  the  best  nail  pocket  a  lather 
can  have  is  made  from  a  portion  of  an  old  boot  leg  cut 
off  to  about  four  inches  deep,  and  having  a  bottom  of 
semi-circular  shape  made  of  wood,  and  to  which  the 
portion  of  the  boot  is  fastened  by  means  of  broad-head- 
ed tacks.  The  pocket  is  fastened  to  the  workman's 
waist  by  means  of  a  strap,  or  other  suitable  device,  and 
hangs  in  front  of  him  in  a  convenient  position.  Some- 
times nail  pockets  are  made  of  canvas,  but  these  are 
not  so  handy,  as  the  top  is  apt  to  close  and  then  nails 
are  difficult  to  get  at.  This  never  occurs  with  the  boot 
leg  pocket. 

Cut-off  Saw. — A  cross-cut  saw  is  an  indispensable 
tool  to  the  lather  for  cutting  lath  in  larger  quantities 
for  short  spaces,  and  for  rigging  up  platforms  to  work 
on,  and  for  cutting  supplementary  studding  or  strips 


TOOLS  AND  APPLIANCES 


59 


where  such  are  necessary.  The  saw  should  have  rather 
coarse  teeth  and  have  plenty  of  set.  Usually,  the  lather 
thinks  that  almost  any  old  used-up  saw  is  good  enough 
for  this  purpose,  and  we  find  him  struggling  away  with 
all  his  strength  cutting  through  a  bundle  of  lath,  when, 
if  he  had  a  saw  that  was  worth  anything — as  a  saw — 
he  would  perform  his  labors  with  about  one-half  the 
effort,  and  one-third  of  the  time.  It  is  all  wrong  to 
think  of  being  able  to  work  satisfactorily  with  inferior 
or  imperfect  tools.  There  is  no  economy  in  using  tools 
of  this  kind,  and  any  lather  who  fancies  he  is  going 
to  make  or  save  anything  by  making  use  of  an  old 
buckled,  mortar-stained  saw,  makes  a  terrible  mistake. 
Get  a  good  saw  and  keep  it  in  good  order,  and  it  will 
pay  you  in  two  weeks.  (See  X,  Fig.  2.)  Besides  these 
enumerated,  there  are  many  other  tools  and  appliances 
that  the  plasterer  will  require,  such  as  jointing  rules, 
moulding  knives,  modelling  tools,  drags,  chisels,  com- 
passes, plumb  rules,  etc. 


PLASTER,  LIME,  CEMENTS,  SAND,  fiTC. 

Plaster  of  Paris. — Gypsum,  from  which  plaster  of 
Paris  is  made,  is  a  sulphate  of  lime,  and  is  so  named 
from  two  Greek  words — ge,  the  earth;  and  epsun,  to 
concoct,  i.  e.,  concocted  in  the  earth.  In  Italy  it  is 
known  by  the  name  of  gesso;  in  Scotland  it  is  called 
stucco;  in  this  country  it  is  known  as  calcined  plaster; 
and  in  the  English  trade  as  plaster.  The  term  plas- 
ter" will  henceforth  be  used  in  this  book.  The  writings 
of  Theophrastus  and  other  Greek  authors  prove  that 
the  use  of  plaster  was  known  to  them.  A  stone,  called 
by  Theophrastus  gypsos,  chiefly  obtained  from  Syria, 
Avas  used  by  the  ancients  for  converting  into  plaster. 
Gypsum  is  mentioned  by  Pliny  as  having  been  used  by 
the  ancient  artists^  and  Strabo  states  that  the  walls  of 
Tyre  were  set  in  gypsum.  The  Greeks  distinguished 
two  kinds — the  pulverulent  and  the  compact.  The  lat- 
ter was  obtained  in  lumps,  which  were  burnt  in  the  fur- 
naces, and  then  reduced  to  plaster,  which  was  used  for 
buildings  and  making  casts. 

Gypsum  is  found  in  most  countries — Italy,  Switzer- 
land, France,  Sicily,  The  United  States,  and  some  of 
the  South  American  States;  also  in  Newfoundland  and 
Canada.  The  latter  is  ,  said  to  be  the  finest  deposits  in 
the  world.  It  is  found  in  England  in  many  places. 
The  finest  gypsum  is  called  ^  ^  alabaster, "  and  is  soft, 
pure  in  color,  and  fragile..  This  white  translucent  ma- 
terial is  a  compact  mass  of  crystalline  grains,  and  is  used 
for  making  small  statuary,  vases,  and  other  ornaments. 
Gypsum  is  found  in  immense  quantities  in  the  tertiary 

60 


PLASTER,  LIME,  ETC. 


61 


strata  of  Montmartre,  near  Paris.  This  gypsum  usual- 
ly contains  10  per  cent,  of  carbonate  of  calcium,  not  al- 
ways in  intimate  union  with  the  sulphate,  but  inter- 
spersed in  grains.  This  sulphate  gives  the  Paris  plas- 
ter some  of  its  most  useful  properties.  Pantin,  near 
Paris,  has  large  beds  of  gypsum,  one  bed  being  hori- 
zontal and  over  37  ft.  thick. 

The  term  plaster  of  Paris''  was  mainly  applied  to 
it  because  gypsum  is  found  in  large  quantities  in  the 
tertiary  deposits  of  the  Paris  basin.  Another  reason 
is  that  lime  and  hair  mortar  is  seldom  used  in  Paris  for 
plaster  work,  plaster  of  Paris  being  used  for  most  kinds 
of  internal  and  external  work.  Plaster  is  known  in  the 
color  trade  as  terra  alba.  Plaster  of  Paris  was  known 
in  England  by  the  same  name  as  early  as  the  beginning 
of  the  thirteenth  century.  The  gypsum,  in  blocks,  was 
taken  from  France,  and  burnt  and  ground  there.  It 
continued  to  be  burnt  and  ground  by  the-  users  until 
the  middle  of  the  nineteenth  century.  The  burning 
w^as  done  in  small  ovens,  and  the  grinding  in  a  mill, 
sometimes  worked  by  horse-power,  or  more  often  by 
hand. 

Plaster  is  the  most  vigorous  as  it  is  the  oldest  vehicle 
for  carrying  down  generation  after  generation  the  mas- 
terpieces of  art  with  Avhich  the  golden  age  of  sculpture 
enriched  the  human  race.  For  reproductive  uses,  plas- 
ter enables  youth  to  contemplate  antiquity  in  its  noblest 
achievements.  Today  plaster  is  revolutionizing  indus- 
trial art  for  us,  and  in  all  probability  for  those  w^ho 
are  to  come  after  us.  Plaster,  lowly  and  cheap,  but 
docile  and  durable,  is  the  connecting  agent  with  this 
greatest  of  men's  endorsement  in  the  past.  Plaster 
thus  employed  in  duplicating  works  of  marble,  pottery, 
and  metal  work,  is  today  extending  the  finest  indus- 


62  CEMENTS  AND  CONCRETES 


tries,  modern  and  ancient.  Plaster  is  one  of  the  best 
known  fire-resisting  materials  for  building  purposes. 
After  the  conflagration  at  Paris,  it  was  found  the  beams 
and  columns  of  wood  which  had  been  plastered  were 
entirely  protected  from  fire.  In  cases  where  limestone 
walls  had  been  ruined  on  the  outside  by  the  flames  pass- 
ing through  the  window  openings,  the  same  walls  in- 
ternally escaped  almost  unscathed  owing  to  their  being 
protected  w^th  plaster.  Plaster  in  some  climates  has 
great  lasting  properties.  The  Egyptians  covered  their 
granite  sometimes,  and  sand  stone  always,  with  a  thin 
coating  of  stucco.  The  Greeks  coated  even  their  mar- 
ble temples  with  plaster,  and  the  plaster  portions  are 
now  in  better  preservation  than  unprotected  masonry, 
particularly  at  Agrigentum  in  Sicily. 

Quick  and  Slow  Setting  Plaster. — M.  Landrin,  in  giv- 
ing the  results  of  his  long  continued  studies  relative 
to  the  different  qualities  of  gypsum,  states  that  the 
more  or  less  rapid  setting  of  plaster  is  due  to  the  mode 
in  which  it  is  burned.  Its  properties  are  very  different 
when  prepared  in  lumps  or  in  powder.  The  former 
when  mixed  in  its  own  weight  of  water  sets  in  five  min- 
utes, while  the  latter  under  similar  conditions  takes  fif- 
teen minutes.  The  reason  probably  is  that  plaster  in 
powder  is  more  uniformly  burned  than  when  it  is  in 
lumps,  which  tends  to  prove  this  fact,  that  when  the 
latter  is  exposed  longer  than  usual  to  the  action  of  heat 
it  sets  more  slowly.  Gypsum  prepared  at  a  high  tem- 
perature loses  more  and  more  of  its  affinity  for  water, 
retaining,  however,  its  property  of  absorbing  its  water 
of  crystallization.  Plaster  heated  to  redness  and  mixed 
in  the  ordinary  manner  will  no  longer  set;  but  if,  in- 
stead of  applying  a  large  quantity  of  water,  the  small- 
est  possible  portion  is  used    (say  one-third  of  its 


PLASTER,  LIME,  ETC. 


63 


weight),  it  will  set  in  ten  or  twelve  hours,  and  becomes 
extremely  hard.  To  prepare  good  plaster^  it  should  not 
be  burned  too  quick  to  drive  off  all  its  moisture,  and 
for  its  molecules  to  lose  a  part  of  their  affinity  for  the 
water.  If  the  plaster  is  exposed  to  heat  until  it  has 
only  lost  7  or  8  per  cent,  of  its  moisture  it  is  useless, 
as  it  sets  almost  immediately.  If,  however,  the  burning 
is  again  resumed,  the  substance  soon  loses  its  moisture, 
and  if  then  exposed  to  the  air  it  very  rapidly  retakes 
its  water  of  crystallization,  and  absorption  continues 
more  slowly.  It  then  sets  slowly,  but  attains  great 
hardness. 

Testing. — The  quality  of  plaster  may  be  tested  by 
simply  squeezing  it  with  the  hand.  If  it  cohere  slight- 
ly, and  keeps  in  position  after  the  hand  has  been  gently 
opened,  it  is  good;  but  if  it  falls  to  pieces  immediately 
it  has  been  injured  by  damp.  Although  plaster  does 
not  chemically  combine  with  more  than  one-fourth  of 
its  vv^eight  of  water,  yet  it  is  capable  of  forming  a  much 
larger  quantity  into  a  solid  mass,  the  particles  of  plas- 
ter being  converted  into  a  network  of  crystals,  mechan- 
ically enclosing  the  remainder  of  the  water.  Sulphate 
of  lime  (plaster)  is  soluble  in  water  to  the  extent  of  1 
part  in  about  450,  the  solubility  being  but  little  influ- 
enced by  temperature.  It  is  on  account  of  this  solu- 
bility in  water  that  cements  which  have  to  a  large  ex- 
tent plaster  for  their  bases  are  incapable  in  this  raw 
state  of  bearing  exposure  to  the  weather.  The  setting 
of  plaster  is  due  to  hydration,  or  its  having  but  little 
water  to  take  up  to  resume  a  state  of  consolidation. 
Plaster  is  used  with  hydraulic  limes  to  stop  the  slaking, 
and  convert  the  lime  into  cement.  These  are  then  called 

selenitic.'' 

In  100  parts  of  gypsum  there  are  46  acid,  lime  32, 


64  CEMENTS  AND  CONCRETES 


and  water  22  parts.  Good  plaster  should  not  begin  to 
set  too  soon,  and  it  should  remain  for  a  considerable 
time  in  a  creamy  state.  When  once  set  it  should  be 
very  hard.  Plaster  should  set  slowly,  as  it  gives  more 
time  for  manipulation,  but  principally  because  one 
which  sets  quickly  and  swells  never  becomes  so  hard 
as  slow-setting  material.  The  quality  of  plaster  can- 
not be  determined  by  its  color,  the  color  being  regu- 
lated by  that  of  the  gypsum ;  but  all  things  being  equal, 
the  whitest  and  hardest  generally  yields  the  best  plas- 
ter. But  as  the  exception  proves  the  rule,  it  may  be 
mentioned  that  some  plasters  (such  as  Howe's)  are  of 
a  delicate  pink  tint,  and  of  a  very  fine  grain,  and  ex- 
ceedingly strong  when  gauged.  This  pink  plaster  is 
much  appreciated  by  many  plasterers  for  making  origi- 
nals, as  owing  to  its  fineness  and  density  it  is  very  suit- 
able for  cleaning  or  chasing  up  models  taken  from  the 
clay,  and  also  for  durable  moulding  pieces.  One  of  the 
whitest  plasters  known,  which  is  also  very  close  in  tex- 
ture, is  that  manufactured  by  Cafl^erata.  For  cast  work 
the  color  of  plaster  is  of  small  moment,  because  the  cast 
work  is  sooner  or  later  colored  with  paint,  and  more- 
over, unfortunately  daubed  over  with  distemper,  or 
worse  still,  with  whitewash.  Coarse  plasters  are  darker 
in  color  than  fine.  Coarse  plasters  of  a  sandy  nature, 
and  which  rapidly  sink  to  the  bottom  when  put  in 
water,  contain  too  much  silica,  or  improperly  burnt 
gypsum,  or  are  derived  from  a  bastard  gypsum,  and 
are  generally  of  a  weak  nature. 

Compressive  and  Adhesive  Strength. — The  compres- 
sive resistance  of  properly  baked  plaster  is  about  120 
lbs.  to  the  square  inch  when  gauged  with  neat  water 
and  160  lbs.  when  gauged  with  lime  water;  thus  show- 
ing that  lime  water  hardens  and  improves  the  affinity 


PLASTER,  LIME,  ETC. 


65 


of  plaster.  The  adherence  of  plaster  to  itself  is  greater 
than  to  stone  or  brick.  The  adhesion  to  iron  is  from 
24  to  37  lbs.  the  square  inch. 

French  Plaster, — A  considerable  quantity  of  French 
plaster  was  formerly  used  in  this  country  but  our  own 
is  more  uniform  in  quality  and  cheaper  in  price,  so  the 
use  of  the  French  material  is  somewhat  limited.  In 
Paris  various  kinds  of  gypsum  mortars  are  in  general 
use,  raw  gypsum  and  other  materials  being  often  inter- 
mixed. They  also  contain  free  carbonate  of  lime,  ac- 
cording to  the  degree  of  heat  to  which  the  raw  stone 
has  been  subjected.  The  Hotel  de  Platres,  in  Paris, 
affords  a  good  illustration  of  the  constructive  uses  to 
which  plaster  can  be  put,  some  of  the  blocks  being 
about  a  hundred  years  old. 

Limes, — Lime  is  one  of  the  most  important  materials 
in  the  building  trades.  Limestone  is  the  general  term 
by  which  all  rocks  are  roughly  classified  which  have 
carbonate  of  lime  for  their  basis.  They  are  obtained 
from  many  geological  formations,  varying  in  quality 
and  chemical  properties.  The  carboniferous  consists 
of  nearly  pure  carbonate  of  lime.  In  the  limestone  of 
the  lias  carbonate  of  lime  is  associated  with  silica  and 
alumina  (common  clay),  in  proportions  varying  from 
10  to  20  per  cent.  Carbonate  of  lime  is  found  in  a  state 
of  chemical  purity  in  rhombohedral  crystals  as  Iceland 
spar.  It  is  also  found  in  six-sided  prisms,  known  to 
mineralogists  as  arragonite.  Its  purest  form  as  a  rock 
is  that  of  white  marble.  Colored  marbles  contain  iron, 
m.anganese,  etc. 

.  The  lias  strata  consists  of  a  thin  layer  of  hard  lime- 
stone separated  by  another  of  a  more  argillaceous  char- 
acter, or  shale,  containing  various  proportions  of  car- 
bonate of  lime. 


66  CEMENTS  AND  CONCRETES 


Hydraulic  Limes, — Hydraulic  limes  are  those  which 
have  the  property  of  setting  under  water  or  in  damp 
places,  where  they  increase  in  hardness  and  insolubil- 
ity. The  blue  lias  limQ  formation  is  that  from  which 
hydraulic  lime  is  principally  made.  This  lime,  while  it 
has  excellent  hydraulic  properties,  can  hardly  be  classed 
as  a  cement.  The  stones  which  produce  these  limes  con- 
tain carbonate  of  lime,  clay,  and  carbonate  of  mag- 
nesia. The  clay  plays  an  important  part  in  giving  hy- 
draulicity  to  the  lime,  consequently  this  power  is  great- 
er in  proportion  to  the  amount  of  clay  contained  in  the 
lime.  The  proportion  of  clay  varies  from  10  to  30  per 
cent.  When  lime  contains  clay  it  is  not  so  easily  slaked 
as  pure  lime,  and  does  not  expand  so  much  in  doing 
so,  and  therefore  does  not  shrink  so  much  in  setting. 

Lias  lime  (called  blue  lias  from  the  color  of  the  stone 
from  which  it  is  produced)  is  very  variable  in  quality 
and  is  generally  of  a  feeble  nature,  but  is  sometimes  of 
an  hydraulic  nature.  M.  Vicat  divides  them  into  three 
classes:  feebly  hydraulic,  ordinary  hydraulic,  and  emi- 
nently hydraulic.  Those  belonging  to  the  first  class 
contain  from  5  to  12  per  cent,  of  clay.  The  slaking 
action  is  accompanied  by  cracking  and  heat.  They  also 
expand  considerably,  and  greatly  resemble  the  fat  limes 
during  this  process.  They  are  generally  of  a  buff  color. 
Those  of  the  second  class  contain  from  15  to  20  per 
cent,  of  clay.  They  slake  very  sluggishly  in  an  hour 
or  so  without  much  cracking  or  heat,  and  expand  very 
little.  They  set  firmly  in  a  week.  The  eminently  hy- 
draulic limes  contain  from  20  to  30  per  cent,  of  clay, 
are  very  difficult  to  slake,  and  only  do  so  after  a  long 
time.  Very  frequently  they  do  not  slake  at  all,  being 
reduced  to  a  powder  by  grinding.  They  set  firmly  in 
a  few  hours,  and  are  very  hard  in  a  month." 


PLASTER,  LIME,  ETC. 


67 


A  natural  hydraulic  lime  is  obtained  from  what  ap- 
pears to  be  a  sedimentary  limestone  that  has  been 
formed  by  being  deposited  from  water  which  held  it  in 
solution.  It  is  very  fine-grained,  and  contains  almost 
no  fossils,  and  scarcely  the  trace  of  a  shell  is  to  be  seen, 
except  at  the  top  and  bottoms  of  the  divisions,  which 
are  four  in  number,  and  in  all  from  9  to  12  ft.  thick. 
"When  first  worked,  the  stone  was  slaked  in  hot  kilns, 
but  now  this  is  effected  by  grinding.  According  to  the 
'^M'Ara"  process,  the  '^lime  shells"  from  the  kiln  are 
ground  in  the  same  way  as  the  clinker  of  Portland  ce- 
ment. Beginning  with  a  stone-breaker,  the  lime  passes 
from  this  to  a  pair  of  chilled  crushing  rollers,  and  final- 
ly to  the  millstones,  after  which  the  powder  is  carried 
by  sere  v-conveyor  and  elevator  to  a  rotary  screen,  12  ft. 
by  4  feet,  covered  with  wire  cloth,  which  retains  and 
returns  to  the  millstones  any  residue  in  excess  of  the 
required  fineness.  Sifting  is  a  very  important  factor  in 
the  process,  as  it  is  scarcely  possible  to  have  the  mill- 
stones so  perfect  that  they  will  not  pass  a  few  large 
particles. 

The  residue  of  imperfectly  ground  lime  will  doubt- 
less slake  when  mixed  with  water,  but  at  long  or  un- 
certain periods,  so  that  it  is  obvious  that  fine  grinding 
is  a  necessity,  and  the  setting  properties  are  not  fully 
and  safely  developed  unless  the  whole  is  finely  pulver- 
ized. With  regard  to  ^^Fat  lime":  the  general  prac- 
tice is  for  lime  producers  to  show  their  lime  as  rich  as 
possible  by  analysis,  and  for  users  to  prefer  a  rich  lime, 
for  the  reason  that  it  makes  a  more  plastic  and  better 
working  mortar  with  the  usual  quantity  of  sand.  Now, 
it  has  been  proved  by  experiments,  many  and  varied, 
and  extending  over  a  long  period,  by  the  most  eminent 
authorities,  French,  German,  English  and  American, 


68  CEMENTS  AND  CONCRETES 


that  this  preference  should  exactly  be  reversed,  and 
that  the  poorer  common  limes  will  make  the  best  mor- 
tar, and  will,  in  a  comparatively  short  time,  show  some 
light  setting  power,  whereas  the  very  rich  limes  never 
take  band,  except  in  so  far  as  they  return  to  their  orig- 
inal condition  of  carbonate  by  the  reabsorption  of  car- 
bonic acid  from  the  atmosphere,  and  by  the  slow  evap- 
oration of  the  water  of  mixture.  If  it  does  not  evapo- 
rate, the  mortar  remains  always  soft.  If  it  evaporates 
too  quickly,  the  mortar  falls  to  powder,  a  result  which 
must  be  in  every  one's  experience  who  has  witnessed 
the  taking  down  of  old  buildings,  and  the  clouds  of 
dust  created  by  the  removal  of  every  stone. 

Some  of  the  stones  from  which  fat  lime  is  produced 
contain  a  portion  of  sand  as  an  impurity.  They  there- 
fore yield  an  inferior  substance.  This,  though  cheaper, 
is  not  so  economical  as  pure  lime,  as  it  does  not  increase 
its  volume  so  much  when  slaked.  The  pure  or^fat  lime 
should  only  be  used  for  plastering,  as  it  is  easily  slaked, 
and  therefore  not  so  liable  to  blister  as  most  hydraulic 
limes.  It  expands  to  double  its  bulk  when  slaked,  and 
can  be  left  and  reworked  again  and  again  without  in- 
juring it. 

The  Romans  are  said  to  have  prepared  their  limes. 
This  ^4ime  putty,''  prepared  by  immersion  for  a  longer 
or  shorter  period — seldom  less  than  three  weeks — before 
being  used,  is  laid  on  in  a  very  thin  coat,  and  gives 
a  hard  skin  to  the  surface.  This  hardness  is  largely,  if 
not  wholly,  due  to  the  fact  that  the  lime  is  laid  on  in 
a  thin  layer  on  the  floating  coat  that  has  already  ab- 
sorbed carbonic  acid  from  the  air„  This  thin  layer  be- 
comes harder  than  the  main  body  of  tke  plaster. 

The  whole  process  of  preparing  lime  and  layiixg  J 
on  the  walls  in  thin  coats,  with  a  considerable  space  o? 


PLASTER,  LIME,  ETC. 


69 


time  between  the  coating,  is  conducive  to  the  ultimate 
hardness  of  the  whole.  The  lime  is  first  slaked,  and 
then  made  into  coarse  stuff,  and  setting  stuff,  all  this 
t'me  being  exposed  to  the  carbonic  acid  of  the  atmos- 
phere. Again,  each  coat  is  lang  exposed  to  the  same 
iijfluence  before  being  covered  with  the  next,  although 
in  marked  contrast  to  the  system  of  using  the  mortar 
in  building. 

Calcination. — The  process  of  ^4ime  burning"  is  car- 
ried out  in  several  different  ways.  But  whether  the 
operation  be  carried  out  in  the  simplest  manner,  or  in 
kilns  constructed  on  the  most  scientific  principles,  it 
will  still  depend  (both  as  regards  the  quality  and  quan- 
tity of  lime  produced)  upon  the  kilnsman,  as  it  is  only 
by  constant  observation  from  day  to  day  that  the  man 
becomes  capable  of  judging  whether  the  proper  ttm-  / 
perature  has  been  reached  or  that  a  correct  opinion 
can  be  formed  as  to  the  effects  produced  by  the  various 
disturbing  causes  which  exert  an  important  influence 
upon  the  working  of  a  kiln,  such  as  its  size,  shape,  the 
quality  of  the  fuel,  and  the  state  of  the  atm.osphere. 
The  kilns  vary  in  size  and  shape  in  different  districts, 
though  they  are  generally  inverted  cones  or  ellipsoids, 
into  which  layers  of  limestone  and  fuel  are  alternately 
thrown.  When  worked  continuously  as  running  kilns, 
the  lime  is  periodically  withdrawn  from  below,  fresh 
quantities  of  fuel  and  stone  being  filled  in  at  the  top. 
When  lime  has  not  been  properly  calcined,  or  ^^dead 
burnt,"  it  will  not  slake  with  water.  This  may  arise 
from  two  causes — from  insufficient  burning,  when  the 
limestone,  instead  of  being  entirely  caustified,  has  only 
been  changed  into  a  basic  carbonate,  consisting  of  two 
equivalents  of  lime  and  one  of  carbonic  acid,  one-half 
only  of  its  carbonic  acid  having  been  expelled.  This 


70 


CEMENTS  AND  CONCRETES 


basic  carbonate,  on  the  addition  of  water,  instead  of 
forming  a  hydrate  of  lime,  and  being  converted  into 
a  fine  and  impalpable  powder,  attended  with  the  pro- 
duction of  a  large  amount  of  heat,  is  changed,  with 
little  elevation  of  temperature,  into  a  mixture  of  hy- 
drate and  carbonate.  In  the  case  of  hydraulic  limes 
which  contain  a  considerable  amount  of  silica,  this 
^'dead  burning''  may  arise  from  the  limestone  having 
been  subjected  to  a  too  high  temperature,  whereby  a 
partial  fusion  of  the  silicate  of  lime  formed  has  been 
produced,  giving  an  impervious  coating  to  the  inner 
portions  of  the  stone,  retarding  the  further  evolution 
of  the  carbonic  acid.  On  this  account  the  eminently 
hydraulic  limes  require  to  be  carefully  calcined  at  as 
low  a  temperature  as  practicable ;  and  hence  it  is  not 
infrequently  found  that  lias  lime  has  been  imperfectly 
calcined.  Pure  limes,  if  subjected  to  an  excessive 
temperature,  exhibit  somewhat  less  tendency  to  com- 
bine with  water  than  is  the  case  with  lime  properly 
calcined.  Caustic  limes  unite  with  water  with  great 
energy,  so  much  so  as  to  evolve  a  very  considerable 
amount  of  heat.  When  water  is  poured  upon  a  piece 
of  well-burnt  lime  heat  is  rapidly  generated,  and  the 
lime  breaks  up  with  a  hissing,  crackling  noise,  the 
whole  mass  being  converted  in  a  short  time  into  a  soft, 
impalpable  powder,  known  as    slaked  lime." 

Slahing. — Chemically  speaking  slaked  lime  is  hydrate 
of  lime — that  is,  lime  chemically  combined  with  a 
definite  amount  of  water.  In  the  process  termed  '^slak- 
ing'' one  equivalent  or  combining  proportion  of  lime 
unites  with  one  equivalent  of  water,  or  in  actual  weight 
28  lbs.  of  lime  combines  with  91  lbs.  of  water  (being 
nearly  in  the  proportion  of  three  to  one)  to  form  37 
lbs.  of  solid  hydrate  of  lime.    The  water  loses  its  liquid 


PLASTER,  LIME,  ETC. 


71 


condition,  and  it  is  to  this  solidification  of  water  that 
the  heat  developed  during-  the  process  of  slaking  is 
partly  due. 

Slaking  is  a  most  important  part  in  the  process  of 
making  coarse  stuff  and  putty  lime.    Unless  the  slak- 
ing is  carefully  and  thoroughly  done,  the  resultant  ma- 
terials are  liable  to     blister'^  or  ^'blow,"  owing  to 
small  particles  still  remaining  in  a  caustic  state.  Blis- 
ters may  not  show  until    a    considerable    time  has 
elapsed.    There  are  three  methods  of  slaking  ^'lump- 
lime" — the  first  by  immersion;  the  second  by  sprint- 
ling  with  water;  and  the  third  by  allowing  the  lime  to 
slake  by  absorbing  the  moisture  of  the  atmosphere. 
Rich  limes  are  capable  of  being  slaked  by  immersion, 
and  kept  in  a  plastic  state.    They  gain  in  strength  by 
being  kept  under  cover  or  water.   Pliny  states  that  the 
Romans  had  such  great  faith  in  this  method  that  the 
ancient  laws  forbade  the  use  of  lime  unless  it  had  been 
kept  for  three  years.    All  rich  limes  may  be  slaked 
by  mixing  with  a  sufficient  quantity  of  water,  so  as  to 
reduce  the  whole  to  a  thick  paste.    Lump  lim.e  should 
first  be  broken  into  small  pieces,  placed  in  layers  of 
about  six  inches  thick,  and  uniformly  sprinkled  with 
water  through  a  pipe  having  a  rose  on  one  end,  or  by 
means  of  a  large  watering-can  having  also  a  rose,  and 
covered  quickly  with  sand.    It  should  be  left  in  this 
state  for  at  least  twenty-four  hours  before  being  turned 
over  and  passed  through  a  riddle.    The  layer  of  sand 
retains  the  heat  developed,  and  enables  the  process  of 
slaking  to  be  carried  out  slowly  throughout  the  miass. 
Any  unslaked  lumps  may  be  put  into  the  middle  of  the 
next  heap  to  be  slaked.    The  quantity  of  water  should 
be  perfectly  regulated,  as  if  over-watered  a  useless  paste 
is  formed.     If  a  sufficient  quantity  is  not  supplied,  ^ 


72  CEMENTS  AND  CONCRETES 


dangerous  powdering  lime*  is  produced.  Slaking  by 
sprinkling  and  covering  the  lime  lumps  is  frequently 
done  in  a  very  imperfect  and  partial  manner,  and  por- 
tions of  the  lime  continue  to  slake  long  after  the  mortar 
has  been  used.  Special  care  must .  be  exercised,  and 
sufficient  time  must  be  allowed  for  the  lime  to  slake 
when  this  method  is  employed. 

Different  qualities  of  lime  require  variable  amounts 
of  water;  but  the  medium  quantity  is  about  a  gallon 
and  a  half  to  every  bushel  of  lime.  No  water  should 
be  added  or  the  mass  disturbed  after  slaking  has  be- 
gun. In  most  places  the  lime  for  making  coarse  st'uff 
is  generally  slaked  by  immersion,  and  is  run  into 
a  pit,  the  sides  of  which  are  usually  made  up  with 
boards,  brick  work,  or  sand,  the  lime  being  put  into 
a  large  tub  containing  water.  When  the  lime  is  slaked, 
it  is  lifted  out  by  means  of  a  pail,  and  poured  through 
a  coarse  sieve.  It  is  sometimes  made  in  a  large  oblong 
box,  having  a  movable  or  sliding  grating  at  one  end  to 
allow  the  lime  to  run  out  and  also  to  prevent  the  sedi- 
ment from  passing  through. 

In  preparing  lime  for  plaster  work,  the  general  prac- 
tice is  to  slake  it  for  three  weeks  before  using.  Not 
only  so,  but  a  particular  cool  lime  is  selected,  for  the 
reason  that  it  is  not  liable  to  blister  and  deface  the 
internal  walls  when  finished.  Now,  while  all  this  pre- 
caution is  taken  in  regard  to  plastering,  in  making  mor- 
tar for  building  the  lime  is  slaked  and  made  up  at 
once,  and  it  is  frequently  -used  within  a  day  or  two. 
But  this  is  not  all.  Limes  which  are  unsuitable  for 
plaster  work,  known  as  hot  limes,  and  which,  when 
plasterers  are  obliged  to  use^  must  be  slaked  for  a 
period  of — not  three  weeks,  but  more — nearly  three 
months  before  using,  and  are  then  not  quite  safe  from 


PLASTER,  LIME,  ETC. 


73 


blistering,  are  the  limes  mostly  used  for  building  pur- 
poses. It  will  at  once  be  seen  that  when  mortars  of 
these  limes  are  used  immediately,  the  unslaked  par- 
ticles go  on  slaking  for  a  long  time,  drying  up  the 
moisture,  and  leaving  only  a  friable  dust  in  the  joints. 
This  should  help  in  understanding  the  old  Roman  law 
which  enacted  that  lime  should  be  slaked  for  three 
years  before  using.  If  three  years  should  seem  to  us 
an  absurd  time,  yet  it  may  be  justly  said  that  at  least' 
three  months  are  required  to  slake  completely,  and  to 
develop  fully  the  qualities  of  many  of  the  common 
limes  in  everyday  use.  Major-General  Gillmore,  the 
eminent  American  specialist  on  the  subject  of  Limes 
and  Cement,  mentions  that  in  the  south  of  Europe  it 
is  the  custom  to  slake  the  lime  the  season  before  it  is 
to  be  used. 

Mortar. — This  is  a  term  used  for  various  admixtures 
of  lime  or  cement,  with  or  without  sand.  For  plaster 
work  it  is  usually  composed  of  slaked  lime,  mixed  with 
sand  and  hair,  and  is  termed  coarse  stuff,"  and  some- 
times ''lime  and  hair,"  also  ''lime."  In  Scotland  the 
coarse  stuff  is  generally  obtained  by  slaking  the  lump 
lime  (locally  termed  shells)  with  a  combination  of 
water  sprinkling  and  absorption.  The  lime  is  placed  in 
a  ring  of  sand,  in  the  proportion  of  one  of  lime  to 
three  of  sand,  and  water  is  then  thrown  on  in  suffi- 
cient quantities  to  slake  the  greater  portion.  The  whole 
is  then  covered  up  with  the  sand,  and  allowed  to  stand 
for  a  day;  then  turned  over,  and  allowed  to  stand  for 
another  day;  afterwards  it  is  put  through  a  riddle  to 
free  it  from  lumps,  and  allowed  to  stand  for  six  weeks 
(sometimes  more)  to  further  slake  by  absorption.  It 
is  next  "soured" — that  is,  mixed  with  hair  ready  for 
use.    Sometimes  when  soured  the  stuff'  is  made  up  in 


74  CEMENTS  AND  CONCRETES 


a  large  heap,  and  worked  up  again  as  required  for 
use.  This  method  makes  a  sound,  reliable  mortar.  In 
some  parts  lime  slaked  as  above  is  mixed  with  an  equal 
part  of  run  lime.  This  latter  method  makes  the  coarse 
stuff  fatter'^  and  works  freer.  All  slaked  limes  have 
a  greater  affinity  for  water  than  the  mechanically 
ground  limes. 

Grinding  is  another  process  for  making  mortar  or 
^  ^  lime, ' '  and  if  made  with  any  kind  of  limestone  is 
beneficial.  It  thoroughly  mixes  the  material,  increases 
the  adhesion,  adds  to  the  density,  and  prevents  blister- 
ing. When  there  is  a  mortar-mill,  either  ground  or 
lump  lime  can  be  used,  and  the  coarse  stuff  may  be 
made  in  the  proportion  of  1  part  lime  and  3  parts 
sand.  The  lime  should  be  left  in  the  mill  until  thor- 
oughly reduced  and  incorporated,  but  excessive  grind- 
ing is  detrimental  The  process  should  not  be  con- 
tinued more  than  thirty  minutes.  Both  mxaterial  and 
strength  is  economized  if  lump  lime  is  slaked  before 
being  put  in  the  mill. 

When  a  mortar-mill  is  used  for  grinding  the  lime, 
the  sand  may  be  partly  or  wholly  dispensed  with,  and 
excellent  results  are  obtained  by  using  old  broken  bricks 
(clean  and  well  burnt),  stone  chippings,  furnace  cin- 
ders (free  from  coal),  or  slag.  It  is  most  essential  in 
all  cases  that  the  materials  used  should  be  perfectly 
clean.  It  should  be  "Borne  in  mind  that  a  complete  in- 
corporation of  the  ingredients  is  essential  in  the  slak- 
ing and  mixing  for  coarse  stuff,  whether  done  by  hand 
or  machine.  The  sand  or  other  material  used  can  be 
tested  by  washing  a  portion  in  a  basin  of  clean  water, 
then  sifting  through  a  fine  sieve.  If  there  is  an  undue 
residue  of  clay,  fine  dust  or  mud  in  the  water  or  sieve, 
the  whole  of  the  aggregate  should  be  washed  or  re- 


PLASTER,  LIME,  ETC. 


75 


jected.  Lias  lime  should  be  mixed  dry  with  sand  and 
damped  down  for  seven  or  ten  days  to  ensure  slaking. 
It  should  not  be  used  fresh  for  floating  or  rendering-. 
Pure  or  rich  limes  are  not  so  well  adapted  for  outside 
work,  or  places  exposed  to  the  action  of  damp,  as  hy- 
draulic limes.  Mortar  should  be  well  tempered  before 
using.  Pliny  states  that  it  was  an  ancient  practice  to 
beat  the  mortar  for  a  long  time  with  a  heavy  pestle 
just  before  being  used,  the  effect  of  which  would  be 
not  only  more  thoroughly  to  mix  the  materials,  but  to 
take  from  the  outside  of  the  sand  the  compound  of 
lime  and  silica  (if  such  had  been  formed  during  the 
period  of  seasoning)  and  by  incorporating  it  with  the 
mass,  dispose  it  more  rapidly  to  consolidate.  Smeaton 
found  that  well-beaten  mortar  set  sooner  and  became 
harder  than  mortar  made  in  the  usual  way.  Mortar 
made  from  hydraulic  limes  should  be  mixed  as  rapidly 
as  is  compatible  with  the  thorough  incorporation  of  the 
materials,  and  used  as  soon  as  practicable  after  mixing, 
because  if  put  aside  for  any  length  of  time  its  setting 
properties  will  deteriorate. 

Pure  limes  may  be  rendered  hydraulic  by  mixing 
them  with  calcareous  clays  or  shales,  which  have  been 
so  altered  by  the  agency  of  heat  that  the  silica  they  con- 
tain has  to  some  extent  assumed  the  nature  of  soluble 
silica.  In  good  coarse  stuff  each  granule  of  sand  is 
coated  over  with  the  lime-paste  so  as  to  fill  the  inter- 
stices; the  lime-paster  is  to  hold  the  granular  sub- 
stances in  a  concrete  form.  If  too  much  lime-plaster 
is  present,  it  is  called  ''too  fat";  if  the  lime-paster  is 
deficient  it  is  ''too  lean''  or  "poor."  This  can  be 
tested  by  taking  up  a  portion  on  a  trowel;  the  "fat" 
will  cling  to  the  trowel  while  the  "lean"  will  run  off 
like  wet  sand.    The  coarse  stuff  can  be  tested  by  mak- 


76  CEMENTS  AND  CONCRETES 


ing  briquettes  and  slowly  drying;  the  good  will  stand 
a  great  pressure,  whereas  the  bad  will  not — in  some 
cases  falling  to  pieces.  Some  coarse  stuff  will  appear 
^^fat"  on  the  trowel^  but  it  may  be  the  fatness  of  mud, 
not  the  fatness  of  lime^  because  sometimes  sand  is 
adulterated  with  fine-screened  earth.  When  this  stuff 
is  made  in  the  form  of  briquettes  and  dried,  it  will  be 
extremely  friable  and  easy  to  crush;  or  if  put  into 
water  until  soft,  the  earthy  matter  can  be  seen.  Fine- 
screened  earth,  when  dry  and  in  bulk,  does  not  seem 
an  objectionable  material;  but  in  a  wet  state  it  is  dirt 
or  mud,  and  should  at  once  be  sent  off  to  the  works. 
All  limes  increase  in  strength  by  the  addition  of  sand, 
being  the  reverse  of  Portland  cement,  which  is  weak- 
ened by  this  addition.  Mr.  Read  made  four  samples 
of  mortar  with  the  proportions  of  ground  lime  and  sand 
as  follows :  ' '  Ground  lime  mixed  with  4,  G,  8  and  10 
parts  of  clean  washed  sand  to  1  part  of  ground  lime 
respectively.  All  set  and  went  hard.  One  of  each 
was  placed  in  water;  that  made  with  4  parts  of  sand 
expanded  and  went  to  pieces;  those  with  6,  8  and  10 
parts  of  sand  remained  whole,  and  continued  to  get 
harder."  The  addition  of  a  small  proportion  of  brick 
dust  to  mortar  will  harden  and  prevent  the  disinte- 
gration of  mortar.  The  proportions  are  1  part  of  brick 
dust,  2  parts  of  sand  and  1  part  of  lime,  mixed  dry 
and  tempered  in  the  usual  way. 

Adhesive  Strength. — The  adhesive  strength  of  mortar 
varies  according  to  the  amount  of  sand  used.  The 
more  sand  used  in  the  mortar,  the  less  its  adhesion. 
The  following  table  shows  the  force  required  to  tear 
apart  bricks  bedded  in  mortar  made  with  the  usual 
proportions  of  sand  at  the  end  of  twenty-eight  days : 


PLASTER,  LIME,  ETC.  77 
Adhesive  Strengths  of  Limes  and  Cements. 


Fat  lime  and  sand 
Common  lias  lime  and  sand 

Portland  cement 

<{  a  (t  (t 


The  old  mortar  which  was  held  in  such  high  esteem- 
by  the  Romans  is  said  to  have  consisted  of  lime  mixed 
w^ith  puzzolana  or  trass.  Trass  is  a  material  similar 
in  its  nature  to  puzzolana,  obtained  from  extinct  vol- 
canoes in  the  valley  of  the  Rhine,  also  in  Holland,  and 
is  largely  employed  in  engineering  works.  The  name 
trass  is  derived  from  a  Dutch  word  meaning  a  binding 
substance.  Much  has  been  written  and  said  about  the 
ancient  and  the  old  Roman  mortars,  but  it  may  be 
safely  said  that,  from  the  year  one  up  to  the  present 
time,  no  cement  or  mortar  has  the  strength,  or  could 
excel,  or  stand  our  variable  climate  as  well  as  Portland 
cement.  The  primary  cause  of  the  premature  decay 
which  takes  place  in  stuccos  and  cements,  when  used 
externally  as  a  coating  to  walls,  is  the  presence  of 
muddy  earth  and  decayed  animal  and  vegetable  matter 
in  the  sand  used  in  the  lime  and  cement.  To  this  may 
be  added  the  frequent  impurities  in  the  limes  and  ce- 
ment themselves.  The  impurities  in  the  sand  may  be 
eradicated  by  a  thorough  washing,  and  the  lime  should 
be  carefully  selected,  prepared  and  manipulated.  Hav- 
ing now  briefly  reviewed  the  principal  parts  and 
process  of  mortar,  the  practical,  conclusions  to  be 
drawn  are,  that  the  quality  of  the  lime  is  of  as  great 
importance  as  the  quantity,  and  thorough  slaking  is 
imperative ;  that  the  proportions  of  sand  may  vary  con- 


(1  to  3)  4%  lbs.  per  Sq.  In. 

il  Q                     ((              ((             U  << 

(lto4)  6%   "     "    "  " 

(lto4)  23      "    "    "  " 

(lto6)  15X   "     "  " 


78 


CEMENTS  AND  CONCRETES 


siderably,  and  that  it  should  be  coarse  and  irregular  in 
size,  and  of  a  clean  and  hard  nature. 

The  Hardening  of  Mortar. — According  to  the  results 
obtained  from  tests  and  experience,  the  hardening  of 
mortar  is  due  to  several  causes  acting  collectively. 
These  causes  appear  to  be  absorption  of  carbonic  acid 
from  the  atmosphere,  and  the  combination  of  part  of 
the  water  with  the  lime  which  act  upon  the  sand,  dis- 
solve and  unite  with  some  of  the  silica  of  the  sand  is 
composed,  thus  forming  a  calcium  silicate  (silicate  of 
lime).  Some  authorities  state  that  the  silicate  of  lime 
is  formed  by  the  reaction  of  lime  and  silicate  of  mor- 
tar, and  to  this  is  due  the  hardness  of  old  mortar.  In 
mortar  from  the  pure  lime,  the  initial  setting  is  due 
to  the  evaporation  of  water,  and  to  the  production  of 
minute  crystals  of  hydrate  of  lime,  which  slowly  ab- 
sorbs carbonic  gas  from  the  air,  the  rapidity  of  this 
absorption  necessarily  decreasing  in  proportion  to  the 
difficulties  presented  to  the  free  access  of  air.  The 
setting  and  hardening  of  hydraulic  limes  are  due  mainly 
to  crystallization  brought  by  the  action  of  water  on 
the  silicate  of  lime  and  not  mere  absorption  of  carbonic 
gas  from  the  atmosphere,  as  is  the  case  of  fat  limes. 

The  Romans  were  convinced  that  it  was  owing  to 
prolonged  and  thorough  slaking  that  their  works  be- 
came so  hard,  and  were  not  defaced  by  cracks.  Al- 
berti  mentions  that  he  once  discovered  in  an  old  trough 
some  lime  which  had  been  left  there  five  hundred 
years,  as  he  was  led  to  believe  by  many  indications 
around  it,  and  that  the  lime  was  as  soft  and  as  fit  to 
be  used  as  if  it  had  been  recently  made.  Common  mor- 
tar made  of  rich  lime  hardens  very  slowly,  and  only 
by  the  evaporation  of  the  water  of  the  mixture,  and  by 
the  absorption  of  carbonic  acid  from  the  atmosphere, 


PLASTER,  LIME,  ETC. 


79 


with  which  it  forms  a  crystalline  carbonate  of  lime. 
This  process,  however,  is  so  slow,  that  it  gave  rise  to 
the  French  proverb  that  ''Lime  at  a  hundred  years  old 
is  still  a  baby'';  and  there  is  a  similar  proverb  among 
Scotch  masons,  ''When  a  hundred  years  are  past  and 
gane,  then  gude  mortar  turns  into  stane. ''  Mortar 
from  the  interior  of  the  pyramids,  where  it  has  been  ex- 
posed to  the  action  of  the  air,  still  contains  free  lime, 
although  it  is  five  thousand  years  old.  It  has  been 
ascertained  that  in  rich  lime  mortars  the  carbonic  acid 
penetrates  about  one-tenth  of  an  inch  into  the  joint  in 
the  first  year,  forming  a  skin  or  film  which  opposes  the 
further  absorption  of  carbonic  acid,  except  at  a  decreas- 
ing ratio,  so  that  the  lime  remains  soft  for  an  indefi- 
nite period.  In  illustration  of  this  several  cases  have 
been  cited,  amongst  others  one  by  General  Treussart, 
who,  in  the  year  1822,  had  occasion  to  remove  one  of 
the  bastions  erected  by  Vauban  in  1666.  After  ihese  156 
years  the  lime  in  the  interior  was  found  to  be  quite 
soft.  Dr.  John,  of  Berlin,  mentions  that  in  removing 
a  pillar  of  9  ft.  diameter  in  the  Church  of  Saint  Peter, 
Berlin,  eighty  years  after  erection,  the  mortar  was  found 
to  be  quite  soft  in  the  interior. 

General  Pasley  mentions  several  instances  at  Dover 
Harbor,  and  at  Chatham  dock  yard,  the  latter  in  par- 
ticular, when  part  of  the  old  wall  was  pulled  down  in 
the  winter  of  1834.  The  workmen  were  obliged  to  blast 
the  brickwork  fronting  the  river,  which  had  been  built 
with  Roman  cement,  but  the  backing,  done  with  common 
lime  mortar,  was  in  a  state  of  pulp;  the  lime  used  had 
been  prepared  from  pure  limestone  or  chalk.  But  it 
is  unnecessary  to  go  back  so  far  for  knowledge  of  the 
absence  of  the  setting  quality  in  the  rich  limes,  as 
there  have  been  frequent  experiences  of  it  in  the  pres- 


80 


CEMENTS  AND  CONCRETES 


ent  age.  While  these  remarks  are  true  of  the  richer 
limes,  many  of  our  limes  are  comparatively  poor  in 
carbonate,  and  associated  with  silica,  alumina,  mag- 
nesia and  oxide  of  iron,  which  may  either  be  partially 
combined  in  the  natural  state,  or  enter  into  combina- 
tion with  the  lime  during  the  process  of  calcination, 
and  these  limes  might  be  termed  slightly  hydraulic. 

M.  Landrin,  who  submitted  to  the  French  Academy 
the  results  of  some  experiments  on  the  hydraulicity  and 
hardening  of  cements  and  lime,  came  to  the  conclusion 
that  (1)  silicates  of  lime  raised  to  high  temperature 
set  with  difficulty,  and  in  any  case  do  not  harden  in 
water;  (2)  for  the  recalcination  of  cements  to  exert 
a  maximum  influence  on  the  setting,  in  connection  with 
water  of  the  compound  obtained,  the  process  must  be 
carried  sufficiently  far  for  the  limes  to  act  on  the  silica 
so  as  to  transform  it  into  hydraulic,  and  not  fused 
silica;  and  (3)  carbonic  acid  is  an  indispensable  factor 
in  the  setting  of  siliceous  cements,  in  as  much  as  it  is 
this  substance  which  ultimately  brings  about  their  hard- 
ening. The  comparative  strengths  of  various  mortars 
are  shown  in  the  following  table: 


PLASTER,^  LIME, 


ETC. 


81 


a;  a; 


is 


^  a 

li 

si 

a; 


be 

<+-(  W 

a: 

dj  o3 


.  o  o  o 

•  +J  +J  ^ 

•  o  ic  ^ 

•  00  00 

odd 


o  o  o  o  o  o 

^  4-»  -M  +J 

T-i  o  o  o  o  ^ 

00  00  CO  O  CD  tH 
tH  tH        tH  tH 


0  0  0 


5c  <U  o 
C  O.  • 

^  Kr, 

tH  <u  rJ.rH 


05  O  CO  J>  ^  ^ 

i>  00  rH  TdH  CO 


J>i>  CO  coooocoooo^ 
(M CO    O  CO  iO  J>  IC 


o  CO  CO 

00  TtH  CO 


cogs 
m  «3  « 


CO 

o  o 

T-5  d 
CO  o 


CO  O  00  tH  <M  i:^ 
lO  00  00  CO  CO  (M 

co'  tJH     i6  ci  no 

CO  lO  rH  CO  CO  05 
(M  T-H  tH  rH  T— ( 


CO  CO 

CO  00  CO 


ater. 

CO  CO 
CO  CO 

CO 
CO 

iO  CO  o  o  o  o 

05  CO  O  IC  O  lO 

O  CO  o 
O  CO  o 

rH  rH 

1—1 

T-H  rH  <M*  tH  (M*  05 

rH*  rH  05 

noNS. 

Lime. 

1.00 
1.00 

1.00 

.   .   .  o  CO  CO 
.   .   .  io  CO  00 

•  •   •  d  d  d 

Loam. 
0.50 
0.66 
0.83 

ment 

o  o  o  o  o  o 
o  o  o  o  o  o 

o  o  o 
o  o  o 

O 

rH  rH  tH  tH  T-i  rH 

rH  rH  rH 

'd 
c 

o  o 
o  o 

o 
o 

o  o  o  o  o  o 
o  o  o  o  o  o 

O  O  O 

o  o  o 

c3 

05 

d  oo' d  d  00  d 

rH  tH 

d  00  d 

rH 

t>  i>  iC  Q  iC  O lO 
tH  05    05    rH  05  CO  i>  i>  00 


rH  JO  Oi 
05  05  tH 


tH  05    CO    rH  05  CO  tH  C5  CO 


82 


CEMENTS  AND  CONCRETES 


Magnesia  in  'Mortars. — Magnesia  plays  an  important 
part  in  the  ''setting''  of  hydraulic  limes  as  well  as  in 
Portland  cement.  Vicat,  after  many  experiments,  was 
led  to  recommend  magnesia  as  a  suitable  ingredient  of 
mortars  to  be  immersed  in  the  sea,  stating  that  if  it 
could  be  obtained  at  a  cost  that  would  admit  its  appli- 
cation to  such  purposes,  the  problem  of  making  con- 
crete unalterable  by  sea  water  would  be  solved.  Gen- 
eral Gillmore,  speaking  of  the  American  lime  and  ce- 
ment deposits,  says:  ''Magnesia  plays  an  important 
part  in  the  'setting'  of  mortars,  derived  from  the  ar- 
gillo-magnesian  limestone  such  as  those  which  furnish 
the  Rosendale  cements.  The  magnesia,  like  the  lime, 
appears  in  the  form  of  a  carbonate.  During  calcination 
the  carbonic  acid  is  driven  off,  leaving  protoxide  of 
magnesia  which  comports  itself  like  lime  in  the  pres- 
ence of  silica  and  alumina,  by  forming  silicate  of  mag- 
nesia and  aluminate  of  magnesia.  These  compounds 
become  hydrated  in  the  presence  of  water,  and  are 
pronounced  by  Vicat  and  Chatoney  to  furnish  gangues, 
which  resist  the  dissolving  action  of  sea  water  better 
than  the  silicate  and  aluminate  of  lime..  This  statement 
is  doubtless  correct,  for  we  know  that  all  of  these  com- 
pounds, whether  in  air  or  water,  absorb  carbonic  acid, 
and  pass  to  the  condition  of  subcarbonates,  and  that 
the  carbonate  of  lime  is  more  soluble  in  water  holding 
carbonic  acid  and  certain  organic  acids  of  the  soil  in 
solution  than  the  carbonate  of  magnesia.  At  all  events, 
whatever  may  be  the  cause  of  the  superiority,  it  is 
pretty  well  established  by  experience  that  the  cements 
derived  from  argillo-magnesian  limestones  furnish  a 
durable  cement  for  construction  in  the  sea." 

In  Marshal  VaiUant's  report  to  the  French  Academy 
of  Sciences,  from  the  Commission  to  which  Chatoney 


PLASTER,  LIME,  ETC. 


83 


and  Rivot's  paper  was  referred  in  1856,  this  superiority 
of  the  magnesian  hydrates  is  distinctly  asserted.  A  few 
years  ago  the  French  Government  Office  of  Civil  En- 
gineers made  a  series  of  comparative  tests  on  three  sam- 
ples each  of  French,  English  and  German  cement,  in 
which  the  results  are  given  in  favor  of  the  German 
cement,  which  contains  magnesia  to  the  extent  of  2.4 
per  cent,  against  0.26  in  the  English  and  0.32  in  the 
French,  and  summed  up  thus:  ^^A  great  value  partly 
due  to  the  higher  percentage  of  magnesia  contained  in 
it."  Gillmore  further  says  that  magnesian  limestone 
furnishes  nearly  all  the  hydraulic  cement  manufactured 
in  the  western  part  of  the  State  of  New  York.  At 
East  Vienna  it  has  been  used  for  cement,  and  at  Akron, 
Erie  County,  N.  Y.,  a  manufactory  of  some  extent  is  in 
operation.  Vicat  says:  Having  analyzed  several  old 
mortars,  with  the  view  of  discovering,  if  possible,  to 
what  their  superior  durability  might  be  attributed,  I 
found,  in  some  excellent  specimens  of  very  old  mortar, 
magnesia  to  exist  in  considerable  proportions."  The 
limestones,  therefore,  from  which  these  mortars  were 
prepared  must  have  contained  the  silica  and  magnesia 
as  constituent  ingredients;  and  it  is  to  be  remembered 
that  it  is  the  presence  of  these  substances  which  com- 
municates the  property  of  hardening  under  water.  Pro- 
fessor Scorgie  says  of  carbonate  of  magnesia:  ^^Mag- 
nesium carbonate  is  a  substance  very  similar  to  carbon- 
ate of  lime;  it  loses  its  carbonic  acid  in  burning,  com- 
bines with  silica,  etc.,  and  behaves  generally  in  the 
same  way  ;  it  does  not  slake,  however,  on  being  wetted, 
but  combines  with  the  water  gradually  and  quietly  sets 
to  some  extent  in  doing  so.  Magnesium  carbonate  com- 
bined with  lime,  reduces  the  energy  of  slaking,  and  in- 
creases that  of  the  'setting'  process;  when  other  sub- 


84  CEMENTS  AND  CONCRETES 


stances  are  present,  its  behavior  and  combination  with 
them  are  similar  to  those  of  lime.  When  carbonate  of 
magnesia  is  present  in  sufficient  quantity,  say  about  30 
per  cent.,  it  renders  lime  hydraulic  independently  of 
and  in  the  absence  of  clay.''  Colonel  Pasley  also,  by 
experiments,  demonstrated  that  magnesium  limestones 
are  suitable  for  hydraulic  mortars. 

The  foregoing  assertions  that  magnesium  carbonate,, 
combined  with  lime,  reduces  the  energy  of  slaking  and 
increases  that  of  the  ^Ssetting''  processes  are  satisfac- 
tory and  conclusive.  Many  such  evidences  showing  the 
value  of  magnesia  in  hydraulic  mortars  might  be  quoted, 
but  perhaps  these  are  sufficient. 

Effects  of  Salt  and  Frost  in  Mortar. — Few  experi- 
ments have  as  yet  been  made  to  test  the  general  effects 
of  salt  in  mortars,  though  as  a  preventive  of  the  effects 
of  frost  it  has  been  tried  with  varying  results. 

In  some  experiments,  designed  to  ascertain  the  effect 
of  frost  upon  hydraulic  limes  and  cement  gauged  with 
and  without  addition  of  salt  to  the  water,  cubes  of  stone 
were  joined  together  with  cement  mixed  with  water 
ranging  from  pure  rainwater  to  water  containing  from 
2  to  8  per  cent,  of  salt.  Before  the  cement  was  set  the 
blocks  were  exposed  in  air  at  a  temperature  varying 
from  20  to  32  degrees  Fahr.,  after  which  they  were 
kept  for  seven  days  in  a  warm  room.  At  the  end  of 
this  time  the  samples  were  examined.  The  cement 
made  with  water  was  quite  crumbled,  and  had  lost  all  its 
tenacity.  The  cement  made  with  water  containing  2  per 
cent,  was  in  better  condition,  but  could  not  be  described 
as  good ;  while  that  containing  8  per  cent,  of  salt  had  not 
suffered  from  its  exposure  to  the  lowest  temperature 
available  for  the  purpose  of  experiment.  It  is  suggested 
as  possible  that  the  effect  of  the  salt  was  merely  to  pre- 


PLASTER,  LIME,  ETC. 


85 


vent  the  water  in  which  it  was  dissolved  from  freezing  at 
the  temperature  named,  and  so  permitted  the  cement 
to  set  in  the  ordinary  way.  But  it  must  be  allowed 
that  in  practice,  salt  dissolved  in  the  water  for  mixing 
mortar  has  been  successfully  used  to  resist  the  effect 
of  frost.  A  solution  of  salt  applied  to  new  plastered 
walls  in  the  event  of  a  sudden  frost  will  protect  the 
work  from  injury.  The  addition  of  a  small  portion 
of  sugar  will  improve  its  adhesion,  and  increase  the 
frost-resisting  powers. 

Salt  takes  up  the  vapors  from  the  atmosphere,  caus- 
ing the  work  to  show  efflorescence,  and  in  some  instances 
to  flake,  especially  in  external  work.  That  some  en- 
gineers believe  there  is  virtue  in  salt  water  is  beyond 
doubt,  because  salt  water  has  been  named  in  their  speci- 
fications for  the  gauging  of  concrete.  Salt  in  Portland 
cement  seems  to  act  somewhat  differently;  as  regards 
efflorescence  it  shows  more  in  this  material  than  in  lime 
mortar.  Salt  should  not  be  used  in  Portland  cement 
work  that  has  to  be  subsequently  painted.  According  to 
the  results  of  tests  of  mortar  used  for  the  exterior 
brick  facing  of  the  Forth  Bridge  piers  below  water  they 
show  a  good  average  tensile  strength.  One  part  of 
Portland  cement  and  one  part  of  sand  were  slightly 
ground  together  in  a  mill  with  salt  water,  and  briquettes 
made  from  this  gauge  gave  an  average  of  365  lbs.  per 
square  inch  at  one  week,  and  510  lbs.  at  five  weeks  after 
gauging.  It  would  be  interesting  to  note  the  condition 
of  this  mortar  a  century  hence,  time  being  the  trying 
test  for  all  mortars. 

A  solution  of  commercial  glycerine  mixed  with  the 
setting  stuff,  or  used  as  a  wash  on  newly  finished  lime 
plaster  work,  is  a  good  preventive  of  the  evil  effects  of 
frost.  Glycerine  solution  may  also  be  used  for  the  same 


86  CEMENTS  AND  CONCRETES 


purpose  on  new  concrete  paving.  Strong  sugar  water 
mixed  with  coarse  stuff  has  some  power  in  resisting 
frost.  The  quantity  depends  upon  the  class  of  lime, 
but  the  average  is  about  8  lbs.  of  sugar  to  1  cubic  yard 
of  coarse  stuff  or  setting  stuff.  The  sugar  must  be  dis- 
solved in  hot  water  and  the  stuff  used  as  stiff'  as  pos- 
sible. 

Sugar  With  Cement, — Sugar  or  other  saccharine  mat- 
ter mixed  with  cement  has  been  tried  with  varying 
success.  It  is  well  known  that  saccharine  is  used  with 
mortars  in  India.  According  to  some  experiments  made 
in  this  country,  the  results  obtained  were  that  the  addi- 
tion of  sugar  or  molasses  delayed  the  setting  of  the 
mortar,  the  retardation  being  greater  when  molasses  was 
used.  When  certain  proportions  were  not  exceeded,  the 
strength  of  the  mixture  was  that  of  the  pure  cement. 
Less  than  2  per  cent,  of  sugar  must  be  added  to  Port- 
land cement,  and  less  than  1  per  cent,  to  Roman,  other- 
wise the  mortar  will  not  hold  together.  The  sugar  ap- 
pears to  have  no  chemical  action  on  the  other  materials, 
crystals  of  it  being  easily  detected  on  the  broken  sur- 
faces, the  increased  binding  power  of  the  cement 
brought  about  by  the  addition  of  sugar  being  due  more 
to  mechanical  than  chemical  causes.  In  my  own  experi- 
ments with  sugar  added  to  Portland  cement  for  cast- 
ing deep  undercut  ornament  figures  and  animals  out 
of  gelatine  moulds,  the  results  at  first  were  very  irregu- 
lar, some  casts  attaining  great  hardness,  while  others 
crumbled  to  pieces.  The  time  of  setting  also  varied 
considerably.  Three  different  brands  of  cement  were 
used,  and  it  was  found  that  the  cement  containing  the 
most  lime  required  more  sugar  than  the  lowest  limed 
cement,  but  the  average  is  about  II/2  per  cent,  of  added 
sugar.    The  sugar  must  be  dissolved  in  the  water  used 


PLASTER,  LIME,  ETC. 


87 


for  gauging.  The  setting  and  ultimate  hardness  is  also 
influenced  by  the  atmosphere.  The  casts  should  be  kept 
in  a  dry  place  until  set  and  dry,  before  exposing  them 
to  damp  or  wet.  Portland  cement  has  a  tendency  (es- 
pecially if  over  limed)  to  *'fur"  gelatine  moulds,  but 
the  sugared  cement  leaves  the  moulds  quite  clean. 

In  experiments  by  Austrian  plasterers,  mixtures  of 
1  part  of  cement  and  3  parts  sand,  and  10  per  cent,  of 
water,  and  of  pure  cement  with  as  much  water  as  was 
necessary  to  give  the  mass  plasticity,  were  prepared. 
From  1  to  5  per  cent,  of  powdered  sugar  was  well  mixed 
with  the  dry  cement.  The  cement  used  was  of  inferior 
quality,  the  sand  being  ordinary  building  sand,  and 
not  the  so-called  ^'normaP'  sand,  which  is  of  a  superior 
quality.  They  were  left  to  harden  in  a  dry  place,  and 
not  under  water.  For  each  series  of  samples  made  with 
sugar  a  comparative  series  without  sugar  was  prepared, 
all  the  samples  being  made  by  the  same  man,  under  the 
same  conditions  and  with  the  same  care.  The  tenacity 
was  ascertained  by  Kraft's  cement-testing  machine.  The 
strength  was  far  below  that  prescribed  and  generally 
obtained.  It  should  be  mentioned  that  the  samples  with 
sugar  (especially  those  of  pure  cement)  showed  a  strong 
tendency  during  the  first  twenty-four  hours  to  combine 
intimately  with  the  smooth  china  plate  on  which  they 
were  placed  to  swell,  and  the  results  of  the  trial  showed 
that  with  mixtures  of  cement  and  sand,  and  by  harden- 
ing in  a  dry  place,  the  binding  effect  may  be  increased 
by  the  addition  of  sugar,  which  reached  its  maximum 
with  from  3  to  4  per  cent,  of  sugar  added.  With  pure 
cement  the  binding  effect  was  not  much  increased.  If 
the  sugar  used  for  gauging  had  been  dissolved,  and  not 
mixed  dry,  the  results  would  have  proved  better. 


88  CEMENTS  AND  CONCRETES 


Sugar  in  Mortar. — Most  writers  have  supposed  that 
the  ''Old  Eoman  Mortars''  contained  strong  ale,  wort, 
or  other  saccharine  matter,  and  it  is  probable  that  the 
use  of  sugar  with  lime  passed  from  India  to  Egypt  and 
Rome,  and  that  malt  or  other  saccharine  matter  was 
used  in  their  mortars.  The  addition  of  sugar  to  water 
enables  it  to  take  up  about  14  times  more  lime  than  water 
by  itself.  The  following  is  an  extract  from  the  Roorkee : 
' '  It  is  common  in  this  country  to  mix  a  small  quantity  of 
the  coarsest  sugar,  'goor,'  or  'Jaghery,'  as  it  is  termed 
in  India,  with  the  water  used  for  mixing  up  mortar. 
Where  fat  limes  alone  can  be  produced  their  bad  quali- 
ties may  in  some  degree  be  corrected  by  it,  as  its  influence 
is  very  great  in  the  first  solidification  of  mortar.  This  is 
attributed  to  the  fact  that  mortars  made  of  shell  lime 
have  stood  the  action  of  the  weather  for  centuries  owing 
to  this  mixture  of  Jaghery  in  their  composition.  Experi- 
ments were  made  on  bricks,  joined  together  by  mortar 
consisting  of  1  part  of  common  shell  lime  to  1^2  of  sand, 
1  lb.  of  Jaghery  being  mixed  with  each  gallon  of  water. 
The  bricks  were  left  for  13  hours,  and  after  that  time 
the  average  breaking  weight  of  the  joints  in  20  trails 
was  61/2  lbs.  per  square  inch.  In  twenty-one  specimens 
joined  with  the  same  mortar,  but  without  the  Jaghery, 
the  breaking  weight  was       lbs.  per  square  inch." 

The  Madras  plasterers  make  most  beautiful  plaster 
work,  almost  like  enamelled  tiles,  the  shell  lime  being 
mixed  with  Jaghery.  The  surface  takes  a  fine  polish 
and  is  as  hard  as  marble,  but  it  requires  a  good  deal  of 
patient  manipulation.  Dr.  Compton  has  made  some  ex- 
periments with  sugar  gauged  with  cements  and  mortars, 
and  says,  ' '  That  in  medicine  there  are  two  kinds  of  lime- 
water,  one  the  common  lime-water,  that  can  be  got  by 
mixing  lime  and  water,  and  it  is  particularly  noted 


PLASTER,  LIME,  ETC. 


89 


that,  add  as  much  lime  as  you  like,  it  is  impossible  to  get 
water  to  dissolve  more  than  half  a  grain  of  lime  in  one 
ounce,  or  about  two  teaspoonfuls  of  water.  But  by  add- 
ing 2  parts  of  white  sugar  to  1  part  of  lime,  there  is  a 
solution  obtained  which  contains  about  14^  times  more 
linie  in  the  same  quantity  of  water.  Here  it  is  to  be  ob- 
served— and  it  is  a  most  important  point — that  there  are 
hot  limes,  such  as  Buxton^  which  if  they  be  incautiously 
mixed  with  them,  will  burn  the  sugar,  make  it  a  deep 
brown  color,  and  convert  it  into  other  chemical  forms, 
and  possibly  destroy  its  value  in  mortar." 

The  Jaghery  sugar  used  in  India  is  sold  in  the  London 
market  at  about  a  penny  a  pound.  Treacle  seems  to  be 
the  most  promising  form  of  saccharine  matter;  beetroot 
sugar  is  not  good  for  limes  or.  cements.  There  is  a  rough 
unrefined  treacle  which  is  very  cheap,  and  it  is  supposed 
would  have  an  excellent  effect. 

Herzf eld  states  that  he  used  coarse  stuff,  consisting  of 
1  part  of  lime  to  3  of  sand,  to  which  about  2  per  cent, 
of  sugar  had  been  added,  to  plaster  some  walls  in  the 
new  building  of  the  Berlin  Natural  History  Museum, 
and  on  the  day  following  he  found  the  lime  plaster  had 
hardened  as  if  gauged  with  plaster.  He  also  found  it 
useful  in  joining  bricks,  and  recommends  the  coarse  stuff 
to  be  fresh  made,  and  not  with  a  great  proportion  of 
water;  and  states  that  good  molasses  will  yield  as  good 
results  as  sugar. 

Lime  Putty. — This  material  is  prepared  in  a  similar 
way  to  run  lime  intended  for  coarse  stuff.  It  is  run 
through  a  finer  sieve  into  a  box  or  pit.  If  the  latter  is 
used  the  interior  should  be  plastered  with  coarse  stuff  to 
prevent  leakage  and  keep  the  putty  clean.  For  good 
work  the  best  class  of  lump  lime  should  be  used.  The 
putty  should  be  allowed  to  stand  for  at  least  three 


90 


CEMENTS  AND  CONCRETES 


months  before  it  is  used.  For  common  work  the  lump 
lime  for  making  coarse  stuff,  putty  and  setting  stuff  is 
often  run  into  one  pit.  The  putty  at  the  end  farthest 
from  the  sieve,  being  the  finest,  is  retained  for  putty  and 
for  making  setting  stuff,  and  the  remainder,  or  coarser 
portion,  being  used  for  coarse  stuff.  In  many  instances 
the  putty  is  left  for  months  in  an  unprotected  state  dur- 
ing the  progress  of  the  building,  which  is  wrong.  It  may 
be  kept  for  an  indefinite  time  without  injury  if  protected 
from  the  atmosphere,  and  therefore  it  should  be  covered 
up  to  resist  the  action  of  the  air,  as  it  absorbs  the  car- 
bonic acid  gas  and  thus  becomes  slightly  carbonated  and 
loses  to  a  certain  extent  its  causticity,  and  consequently 
its  binding  and  hardening  properties. 

Pliny  states  that  the  old  Roman  limes  were  kept  in  cov- 
ered pits.  If  a  small  portion  is  taken  off  the  top  of  the 
putty  it  will  be  found  not  only  dry,  but  scaly,  short  and 
inert ;  whereas  a  portion  taken  from  the  middle,  or  up  to 
the  part  carbonated,  will  be  found  to  be  of  an  oily  and 
tenacious  nature.  A  cute  plasterer  always  selects  the 
putty  furthest  from  the  sieve  for  mitring  purposes,  as  it 
is  the  finest. 

Setting  Stuff, — This  material  is  composed  of  lime 
putty  and  washed  fine  sharp  sand.  The  proportion  of 
sand  varies  according  to  the  class  of  lime  and  kind  of 
work,  but  the  average  is  3  parts  of  sand  to  1  of  putty. 
The  various  proportions  are  given  where  required  for  the 
different  works.  Setting  stuff  is  used  for  finishing  coat 
of  lime  plastering.  It  is  generally  made  on  a  platform, 
of  scaffold  boards,  and  sometimes  in  a  bin.  The  putty 
and  sand  are  thoroughly  mixed  together  by  aid  of  a 
larry.  The  sand  should  be  sized  by  washing  it  through  a 
sieve  having  a  mesh  of  the  desired  size.  In  some  districts 
it  is  made  by  pressing  or  beating  the  putty  and  sand 


PLASTER,  LIME,  ETC. 


91 


through  a  ' '  punching  sieve ' '  into  a  tub.  Setting  stuff  is 
less  liable  to  shrink  and  crack,  and  is  improved  generally 
if  it  is  allowed  to  stand  after  being  made  until  nearly 
hard,  but  not  dry,  and  then  ''knocked  up"  to  the  re- 
quired consistency  with  water  (preferably  lime-water) 
and  the  aid  of  a  shovel  and  larry.  While  the  stuff  is 
firming  by  evaporation  it  should  be  covered  up  to  protect 
it  from  dust  and  atmospheric  influences.  It  should  be 
used  as  soon  as  ''knocked  up."  Setting  stuff  may  be 
colored  to  any  desired  tint,  and  also  mixed  with  various 
ingredients  to  obtain  a  brilliant  and  marble-like  surface. 

Haired  Putty  Setting. — Haired  putty  was  formerly 
used  to  a  very  considerable  extent  as  a  setting  coat  in 
districts  where  the  local  lime  was  of  a  strong  or  hydraulic 
nature,  not  very  readily  manipulated  when  mixed  with 
sand,  as  used  for  setting  stuff.  This  material  is  com- 
posed of  fine  lime  putty  and  well-beaten  white  hair.  The 
hair  was  thoroughly  mixed  with  the  putty  to  tougheii 
and  prevent  it  from  cracking.  To  such  an  extent  was  hair 
^dded  that  in  some  instances  the  setting  coat  when 
broken  had  the  appearance  of  white  felt.  This  class  of 
setting  stuff  is  now  seldom  used. 

Lime  Water. — This  water  has  many  medicinal  virtues, 
and  is  a  simple  and  inexpensive  remedy  for  cuts  and 
bruises.  Plasterers  are  generally  healthy  and  free  from 
any  infectious  diseases.  This  may  be  partly  owing  to 
their  almost  constant  contact  with  lime.  Lime  water, 
used  as  a  wash,  will  harden  plaster  casts.  It  is  also  used 
when  scouring  and  trowelling  setting  stuff  to  harden  the 
surface. 

Hair. — Hair  is  used  in  coarse  stuff  as  a  binding  me- 
dium, and  gives  more  cohesion  and  tenacity.  It  is  usu- 
ally ox-hair  (sometimes  adulterated  with  the  short  hair 
of  horses).    Good  hair  should  be  long,  strong  and  free 


92  CEMENTS  AND  CONCRETES 


f  rom  grease  or  other  impurities.  It  is  generally  obtained 
in  a  dry  state  in  bags  or  bundles.  This  dry  hair  should 
be  well  beaten  with  two  laths  to  break  up  the  lumps,  as, 
unless  the  lumps  are  thoroughly  broken  so  as  to  sepa- 
rate the  hair  they  are  only  a  waste,  and  worse  than  no 
hair  at  all,  since  the  lumps  have  no  binding  power  and 
will  cause  a  soft  weak  spot  in  the  plaster  when  laid. 
Many  failures  of  ceilings  have  been  caused  by  the  hair 
not  being  properly  beaten  and  mixed.  Human  hair  is 
sometimes  used  for  jerry  work.  Goats'  hair  is  often  used 
here.  Hair  is  usually  obtained  direct  from  the  tanners' 
yard,  fresh  and  in  a  wet  state.  This  makes  the  best 
work,  as  it  is  much  stronger  and  mixes  freely.  Hair 
should  never  be  mixed  with  hot  lime,  and  with  no  mor- 
tars until  nearly  ready  for  using,  because  wet  or  hot 
lime  weakens  the  hair,  more  especially  if  dry.  Coarse 
stuff  for  first  coating  on  lath  work  requires  more  hair 
than  for  brick  or  stone  work.  When  coarse  stuff  is  made 
in  a  mill  the  hair  should  not  be  added  until  the  stuff  is 
ground,  as  excessive  grinding  injures  it. 

Fibrous  Substitutes  for  Hair. — -Manila  fiber  as  a  sub- 
stitute for  hair  in  plaster  work  has  been  the  subject  of 
experiments  in  this  country.  One  of  the  most  conclu- 
sive of  these  tests  was  made  by  four  briquettes  or  plates 
of  equal  size,  one  containing  manila  hemp,  a  second  sisal 
hemp,  a  third  jute  and  a  fourth  goats'  hair  of  the  best 
quality.  The  ends  of  the  plates  were  supported  and 
weights  suspended  from  the  middle.  The  result  showed 
that  plaster  mixed  with  goats'  hair  broke  at  1441/2 
lbs.  weight,  the  jute  at  145  lbs.,  the  sisal  at  150,  and  the 
manila  at  195,  in  the  latter  case  the  hemp  not  breaking, 
but  cracking,  and  though  cracked  in  the  center,  the  lower 
half  of  this  plate,  when  it  was  suspended,  held  onto  the 
upper  half,  the  manila  securing  it  fast.   The  three  other 


PLASTER,  LIME,  ETC.  93 

plates  were  broken — that  is,  the  two  parts  of  each  plate 
had  severed  entirel}^.  Another  experiment  consisted  in 
mixing  two  barrelfuls  of  mortar,  each  containing  equal 
portions  by  measure  of  sharp  sand  and  lime,  one  of  the 
barrels,  however,  being  mixed  with  a  proper  quantity  by 
measure  of  manila  hemp,  cut  in  lengths  of  1^2  to  2 
inches,  and  the  other  of  best  goats '  hair.  On  being  thor- 
oughly mixed  with  the  usual  quantity  of  water,  the  re- 
spective compounds  were  put  in  the  barrels  and  stored 
away  in  a  dry  cellar,  remaining  unopened  for  nine 
months.  On  examination  the  hair  mortar  crumbled  and 
broke  apart,  very  little  of  the  hair  being  visible,  showing 
that  the  hair  had  been  consumed  by  the  action  of  the 
lime ;  .but  the  other,  containing  the  hemp,  showed  great 
cohesion.  It  required  quite  an  effort  to  pull  it  apart, 
the  hemp  fiber  permeating  the  mass  and  showing  little 
or  no  evidence  of  any  injury  done  to  it  by  the  lime. 

Sawdust  as  a  Substitute  for  Hair. — Sawdust  has  been 
used  as  a  substitute  for  hair,  also  for  sand  in  mortar  for 
wall  plastering.  It  makes  a  cheap  additional  ^aggregate 
for  coarse  stuff.  Sawdust  mortar  stands  the  effects  of 
rough  weather  and  frost  when  used  for  external  plaster- 
ing. The  sawdust  should  be  used  dry  and  put  through  a 
coarse  sieve  to  exclude  large  particles.  I  have  used  it 
with  plaster  for  both  run  and  cast  work.  It  proved  use- 
ful for  breaks  of  heavy  cornices  by  rendering  the  work 
strong  and  light  for  handling.  Some  kinds  require  soak- 
ing or  washing,  otherwise  they  are  liable  to  stain  the 
plaster.  Several  patents  have  been  issued  in  America  for 
the  use  of  sawdust  in  place  of  hair  and  of  sand.  One  of 
these  is  for  the  use  of  equal  parts  of  plaster,  or  lime  and 
sawdust ;  another  is  for  the  use  of  4^/2  parts  each  slaked 
lime  and  sawdust  to  1  part  of  plaster,  14  P^^t  of  glue 
and  1-16  part  of  glycerine,  with  a  small  part  of  hair. 


94 


CEMENTS  AND  CONCRETES 


Kahl's  patent  plaster  consists  of  35  per  cent,  of  saw- 
dust, 35  per  cent,  of  sand,  10  per  cent,  of  plaster,  10  per 
cent,  of  glue,  and  10  per  cent,  of  whiting. 

Sand. — Sand  is  the  most  widely  distributed  substance 
in  nature,  not  only  in  the  mineral  but  also  in  the  animal 
and  vegetable  kingdoms.  Clay  contains  no  silica  (the 
chemical  name  for  sand).  Sand  is  the  siliceous  particles 
of  rocks  containing  quartz,  production  by  the  action  of 
rain,  wind,  wave  and  frost.  Some  kinds  of  sand  are  also 
found  inland;  the  deposits  mark  the  sites  of  ancient 
beaches  or  river  beds.  Sand  is  classed  under  various 
heads,  viz.,  calcareous,  argillaceous  and  metallic.  Sand 
varies  in  color  according  to  the  metallic  oxides  contained 
in  them.  Few  substances  are  of  more  importance  than 
sand  for  plastic  purposes.  Its  quality  is  of  primary  im- 
portance for  the  production  of  good  coarse  stuff,  set- 
ting stuff,  and  for  gauging  with  Portland  or  other 
cements  used  for  plaster  work.  Its  function  is  to  induce 
the  mortar  or  cement  to  shrink  uniformly  during  the 
process  of  setting,  hardening  or  drying,  irregular  shrink- 
age being  the  general  cause  of  cracking.  Sand  is  also  a 
factor  in  solidity  and  hardness;  while  being  of  itself 
cheaper  and  used  in  a  larger  proportion  than  lime  or 
cement,  it  decreases  the  general  cost  of  materials.  There 
are  three  kinds — pit,  river  and  sea  sands.  They  gen- 
erally ccnitain  more  or  less  impurities,  such  as  loam, 
clay,  earth  and  salts,  necessitating  their  being  well 
washed  in  water,  more  especially  for  the  finishing  coats 
of  plaster  or  cement  work.  Pit  sand  is  sometimes  found 
quite  clean;  it  is  generally  sharp  and  angular.  River 
sand  is  fine  grained,  not  so  sharp  as  pit  sand,  but  makes 
good  setting  stuff.  Sea  sand  varies  in  sharpness  and 
size,  and  for  plastering  it  should  be  washed  to  free  it 
from  saline  particles  which  cause  efflorescence. 


PLASTER,  LIME,  ETC. 


95 


Regarding  the  use  of  sand  in  mortars,  it  may  almost 
be  spoken  of  as  a  necessary  evil.  Sand  is  necessary  to 
give  body  and  hardness  to  an  otherwise  too  soft  and 
plastic  material,  and  the  coarser  and  cleaner  the  better, 
as  the  coarse  particles  allow  the  carbonic  acid  to  pene- 
trate further  into  the  body  of  the  mortar,  and  assist  in 
the  hardening  process  for  this  reason.  In  the  case  of 
cements  of  all  kinds  sand  is  only  good  for  lessening  the 
cost  of  the  aggregate,  and  in  the  case  of  the  majority  of 
sands  in  daily  use  in  most  places  the  strength  is  reduced 
out  of  all  proportion  to  the  saving  effected.  Brunei,  in 
the  Thames  Tunnel,  was  so  convinced  of  this  that  he  used 
pure  Portland  cement  in  the  arches;  and  General  Pas- 
ley,  treating  of  this,  recommends  that  only  pure  cement 
should  be  used  on  all  arduous  works. 

As  to  the  quality  of  sands,  they  are  of  very  wide 
variety — so  much  so,  that  1  part  of  an  inferior  or  soft 
clayey  sand  will  reduce  the  strength  of  mortar  as  much 
as  3  or  4  parts  of  clean  sharp  granitic  sand.  This  is  well 
exemplified  in  the  sand  test,  which  is  made  with  what  is 
called  standard  sand,  being  a  pure  silecious  sand  sifted 
through  a  sieve  of  400  holes  to  the  square  inch  and  re- 
tained on  one  of  900. 

Good  sand  for  lime  plaster  should  be  hard,  sharp^ 
gritty  and  free  from  all  organic  matter.  For  coarse  stuff 
and  cement  for  floating  coats  it  should  not  be  too  fine. 
Good  sand  for  plaster  work  may  be  rubbed  between  the 
hands  without  soiling  them.  The  presence  of  salt  in  sand 
and  water  is  found  not  to  impair  the  ultimate  strength  of 
most  mortars;  nevertheless  it  causes  an  efflorescence  of 
white  frothy  blotches  on  plaster  surfaces.  It  also  ren- 
ders the  mortar  liable  to  retain  moisture. 

Pine-grained  sand  is  best  for  hydraulic  lime;  the 
coarse-grained  is  best  for  fat  limes,  and  coarse  stuffs  and 


96  CEMENTS  AND  CONCRETES 


Portland  cements  for  floating.  Sand  should  not  be  nni- 
form  in  size,  but,  like  the  aggregate  for  concrete,  should 
vary  in  size  and  form.  A  composition  of  fine  and  coarse 
sand  for  coarse  stuff,  unless  the  sand  is  naturally  so 
mixed,  gives  the  best  results,  for  as  the  lime  will  receive 
more  sand  in  that  way  without  losing  its  plasticity  it  will 
make  a  harder  and  stronger  material,  whether  coarse 
stuff,  setting  stuff  or  for  Portland  cement  work.  If  there 
is  plenty  of  fine  sand  and  a  scarcity  of  coarse  sand,  they 
should  be  mixed  in  the  proportion  of  2  of  coarse  to  1  of 
fine.  If  on  the  other  hand,  there  is  plenty  of  coarse 
sand  and  a  scarcity  of  fine,  they  should  be  mixed  in  the 
proportions  of  2  of  fine  to  1  of  coarse.  The  proportion  of 
sand  varies  according  to  the  different  kinds  and  qualities 
of  limes  and  cements,  also  purposes.  Baryte  is  some- 
times used  as  a  substitute  for  sand.  Silver  sand  is  used 
for  Portland  cement  work  when  a  light  color  and  a  fine 
texture  is  required. 

Mastic. — Mastic  was  formerly  extensively  used  foi 
various  purposes  in  which  now  Portland  cement  is  chiefly 
employed.  It  is  still  used  sometimes  for  pointing  the 
joint  between  the  wood  frames  of  windows  and  the  stone 
work.  Mastic  is  waterproof,  heat-resisting  and  adheres 
to  stone,  brick,  metal  and  glass  with  great  tenacity.  Mas- 
tic is  made  in  various  ways.  Some  plasterers  make  their 
own. 

Scotch  Mastic  is  composed  of  14  parts  of  white  or 
yellow  sandstone,  3  parts  of  whiting  and  1  part  of  lith- 
arge. These  are  mixed  on  a  hot  plate  to  expel  any  mois- 
ture and  then  sifted  to  exclude  any  coarse  particles.  It 
is  then  gauged  with  raw  and  boiled  linseed  oil  in  the 
proportion  of  2  of  raw  to  1  of  boiled  oil.  The  sandstone 
is  pounded  or  ground  to  a  fine  powdered  state  before 


PLASTER,  LIME,  ETC. 


97 


bein^  mixed.  The  surface  to  be  covered  is  first  brushed 
with  Jinseed  oil. 

Common  Mastic  is  prepared  as  follows :  100  parts  of 
ground  stone,  50  parts  silver  sand  or  of  fine  river  sand, 
and  15  parts  of  litharge.  These  are  all  dried  and  mixed 
and  passed  through  a  fine  sieve;  it  then  resembles  fine 
sand.  This  mastic  may  be  kept  for  any  length  of  time  in 
a  dry  place.  When  required  for  use  it  is  gauged  with 
raw  and  boiled  linseed  oil  (in  equal  proportions)  until 
of  the  consistency  of  fine  stuff.  It  requires  long  and  fre- 
quent beating  and  kneading — in  fact,  the  more  it  is 
knocked  up  the  better  it  works.  Its  fitness  for  use  can 
be  ascertained  by  smoothing  a  portion  of  the  gauge^with 
a  trowel.  If  there  are  any  separate  parts  of  the  differ- 
ent materials  or  bright  spots  seen  the  knocking-up  must 
be  renewed  until  it  is  of  even  texture.  The  addition  of  15 
parts  of  red  lead  is  sometimes  used  to  increase  the  tenac- 
ity of  the  mastic. 

*  Mastic  Manipulation. — The  walls  are  prepared  for 
mastic  by  raking  out  the  joints  and  sweeping  with  a 
coarse  broom,  and  the  brick  work  well  saturated  with  lin- 
seed oil.  Narrow  screeds  about  1  inch  wide  are  formed  in 
plaster  to  act  as  guides  for  floating  the  work  plumb  and 
level.  When  laying  the  mastic  it  must  be  firmly  pressed 
on  and  the  floating  rule  carefully  passed  over  the  sur- 
face until  it  is  straight  and  flush.  The  screeds  are  next 
cut  out  and  the  spaces  filled  in  with  extra  stiff  mastic. 
The  whole  surface  is  then  finished  with  a  beech  or  syca- 
more hand  float,  leaving  a  close  and  uniform  texture. 
Mastic  moldings  are  first  roughed  out  with  Medina  or 
other  quick-setting  cement.  The  running  mold  is  muffled 
so  as  to  allow  14  i^ch  for  the  mastic  coat. 

Hamelein^s  Mastic. — This  mastic  consists  of  sand  and 
pulverized  stone,  china,  pottery,  shard,  to  which  are 


98  CEMENTS  AND  CONCRETES 


added  different  oxides  of  lead,  as  litharge,  gray  oxide 
and  minium,  all  reduced  to  powder,  to  which  again  is 
added  pulverized  glass  or  flint  stone,  the  whole  being 
intimately  incorporated  with  linseed  oil.  The  propor- 
tions of  the  ingredients  are  as  follows:  To  any  given 
weight  of  sand  or  pulverized  pottery  ware  add  two-thirds 
of  the  weight  of  pulverized  Portland,  Bath  or  any  other 
stone  of  the  same  nature.  Then  to  every  550  lbs.  of  this 
mixture  add  40  lbs.  of  litharge,  2  lbs.  of  pulverized  glass 
or  flint  stones,  1  lb.  of  minium  and  2  lbs.  of  gray  oxide 
of  lead.  The  whole  must  be  thoroughly  mixed  together 
and  sifted  through  a  sieve,  the  fineness  of  which  will  de- 
pend on  the  different  purposes  for  which  the  mastic  is 
intended.  The  method  of  using  is  as  follows :  To  every 
30  lbs.  of  the  mastic  add  1  quart  of  linseed  oil  and  well 
mix  together  either  by  treading  or  with  a  trowel.  As  it 
soon  begins  to  set,  no  more  should  be  mixed  at  a  time 
than  is  requisite  for  present  use.  Walls  or  other  sur- 
faces to  be  plastered  with  this  material  must  first  be 
brushed  with  linseed  oil. 

Mastic  Cement, — Mix  60  parts  of  slaked  lime,  35  parts 
of  fine  sand  and  3  parts  of  litharge,  and  knead  them  to 
a  stiff  mass  with  7  to  10  parts  of  old  linseed  oil.  The 
whole  mass  must  be  well  beaten  and  incorporated  until 
thoroughly  plastic.  This  mastic  cement  assumes  a  fine 
smooth  surface  by  troweling.  It  is  impervious  to  damp 
and  is  not  affected  by  atmospheric  changes. 


TERMS  AND  PROCESSES. 


The  following  descriptions  are  suited  to  niost  locali- 
ties, though  there  are  districts  in  the  East  and  South 
that  vary  somewhat  from  the  processes  as  described; 
the  difference,  however,  is  so  trifling  that  the  regular 
plasterer  will  have  no  trouble  in  reconciling  such  differ- 
ences. 

Three-Coat  WorkA — Three-coat  work  is  usually  speci- 
fied by  architects  for  all  good  buildings,  but  sometimes 
two-coat  work  is  specified  for  inferior  rooms,  closets,  at- 
tics or  cellars  in  the  same  building.  Three-coat  work 
makes  a  straight,  smooth,  strong  and  sanitary  surface  for 
walls  and  ceilings  when  properly  executed.  The  follow- 
ing is  the  process  for  three-coat  work,  which  consists  of 
first-coating,  floating  and  setting. 

First-Coating. — ''First-coating"  is  termed  in  the 
United  States  ' '  scratch-coating. ' '  It  is  executed  by  lay- 
ing and  spreading  a  single  coat  of  coarse  stuff  upon  the 
walls  and  ceilings  to  form  a  foundation  for  the  subse- 
quent floating  and  setting  coats.  Coarse  stuff  for  /irst- 
coating  should  be  uniformly  mixed  or  ''knocked  up,"  as 
commonly  called.  It  should  contain  more  hair  than  that 
used  for  floating,  so  as  to  obtain  a  strong  binding  key  on 
the  lath-work  and  form  a  firm  foundation  for  the  float- 
ing coat.  Coarse  stuff  may  be  tested  by  lifting  some 
from  the  heap  on  the  point  of  a  trowel.  If  it  is  suffi- 
ciently haired  and  properly  mixed  the  stuff  should  cling 
to  the  trowel  when  held  up  and  the  hairs  should  not  be 
more  than  1-16  inch  apart.  It  should  be  stiff  enough  to 
cling  and  hold  up  when  laid,  yet  sufficiently  soft  and 

99 


100  CEMENTS  AND  CONCRETES 


plastic  to  go  through  the  interstices  between  the  laths. 
Unless  the  stuff  is  made  to  the  proper  consistency  it  will 
''drop" — that  is,  small  patches  where  the  excess  water 
accumulates  or  at  weak  or  too  wide  spaced  laths  will  fall 
soon  after  being  laid. 

When  first-coating  ceilings,  the  coarse  stuff  should  be 
laid  diagonally  across  the  laths,  a  trowelful  partly  over- 
lapping the  previous  one,  the  one  binding  the  other.  By 
laying  the  stuff  diagonally  the  laths  yield  less,  present  a 
firmer  surface  and  are  not  so  springy  as  when  laid  across 
or  at  right  angles  to  them.  Laying  the  stuff  diagonally 
and  overlapping  each  trowelful  helps  to  retain  the  stuff 
in  its  place,  which  otherwise  is  apt  to  ''drop.''  The  stuff 
should  be  laid  on  with  a  full-sized  laying  trowel,  using 
sufficient  pressure  to  force  it  between  the  laths  and  to 
go  sufficiently  through  to  form  a  rivet  and  lap  or  clinch 
on  the  upper  sides  of  the  lathing.  The  stuff  should  be 
laid  fair  and  as  uniform  in  thickness  as  possible.  The 
thickness  should  not  exceed  %  inch  or  be  less  than  % 
inch.  If  too  thick  it  tends  to  weigh  down  the  lath  work 
and  is  apt  to  crack ;  if  too  thin  the  subsequent  scratching 
is  liable  to  cut  the  coat  down  or  nearly  to  the  laths,  thus 
leaving  a  series  of  small  detached  pats  which  are  un- 
stable and  form  a  weak  foundation  for  the  floating  coat 
and  are  a  source  of  cracks  and  often  the  cause  of  the 
w^ork  falling  when  subjected  to  vibration.  A  thickness 
of  y2  inch  gives  the  best  results. 

Scratching. — Scratching  is  sometimes  termed  "scor- 
ing," also  "keying."  It  is  done  with  a  wooden  or  iron 
scratch,  which  may  have  from  one  to  five  points. 
Scratching  is  scoring  the  surface  of  the  first  coat  to 
obtain  a  key  for  the  following  coat.  The  first-coating 
should  be  allowed  to  stand  for  an  hour  or  two  to  allow 
the  stuff  to  get  firm  before  proceeding  with  the  scratch- 


TERMS  AND  PROCESSES  101 


ing.  If  scratched  while  the  stuff  is  soft  it  is  apt  to  drop, 
and  unless  a  man  is  careful  and  light  in  his  working  the 
scratch  will  go  too  deep  and  weaken  the  body  and  the 
rivets  of  first-coating.  A  wide  scratch  should  be  slightly 
angular  at  the  points;  if  square,  it  should  be  drawn 
across  the  work  in  a  slanting  position  so  as  to  give  an 
undercut  key.  The  whole  of  the  surface  should  be  uni- 
formly scratched  with  a  moderately  sharp  pointed 
scratch.  The  surface  should  be  cross-scratched  diag- 
onally. Square  scratching  cuts  and  weakens  the  rivets, 
especially  when  the  scratch  is  drawn  in  the  same  line  as 
the  laths.  Good  work  is  generally  scratched  with  a  sin- 
gle lath.  This,  like  other  scratches,  should  be  drawn  in 
a  slanting  position,  so  as  to  give  an  undercut  score.  Sin- 
gle scratches  is  the  best  way  for  circular  surfaces.  First 
score  it  diagonally  across  the  laths  and  then  crossways 
diagonally,  keeping  the  scoring  rather  square  than  loz- 
enge-shaped. When  too  pointed  the  acute  angles  are 
liable  to  be  broken  when  laying  the  floating  coat.  The 
scores  should  not  be  more  than  I14  inch  from  center  to 
center,  or  less  than  one  inch  from  center  to  center.  Close 
scoring  weakens  the  body  of  the  first-coating,  while  wide 
scoring  affords  insufficient  key.  Scratching  with  a  single 
lath  requires  thrice  or  even  more  time  than  if  done  with 
a  four  or  five  pointed  scratch,  but  the  work  is  stronger, 
as  the  body  and  the  rivets  of  the  first  coating  are;  not 
cut  too  deep  or  otherwise  weakened.  In  some  instancies — 
such  as  a  thin  body  of  first-coating  already  mentioned — • 
the  scoring  is  so  deep  that  the  body  of  the  work  is  cut 
into  a  series  of  detached  parts.  By  using  a  single  lath 
or  point  the  scoring  is  also  more  uniform  and  better  un- 
dercut, thus  obtaining  a  stronger  surface  and  a  better 
key  for  the  floating;  coal^.^  The  e^cMjtionjal  time  required 
for  '^single  scx'atGhing\\shouJri  be  caken  mto  x}oi:j^^^ 


102  CEMENTS  AND  CONCRETES 


tion,  and  annotated  and  allowed  for  when  making  speci- 
fications and  estimating.  All  scratching  should  be  done 
uniformly,  taking  care  not  to  miss  any  parts,  especially 
round  door  and  window  frames,  wood  grounds  or  where 
there  may  be  jarring  or  vibration.  On  the  regular  and 
proper  scratching  depends  the  key  and  stability  of  the 
succeeding  coats.  Scratching  with  the  point  of  a  trowel 
should  not  be  permitted.  The  use  of  a  trowel  as  a 
scratch  is  detrimental  to  the  strength  of  the  stuff  and  the 
key.  The  sharp  edge  of  the  trowel  cuts  the  hair  and 
thus  weakens  the  stuff.  The  smooth  and  thin  plate  of  the 
trowel  leaves  a  smooth  and  narrow  key;  the  smooth  side 
of  the  key  presents  no  attachment  for  the  second  coat, 
while  the  deep  part  of  the  key  is  too  narrow  to  receive 
its  due  portion  of  stuff  to  fill  it  up,  thus  leaving  a  space 
for  contained  air  and  a  more  or  less  hollow  and  unsound 
body. 

Rendering, — The  first  coat  on  brick,  stone  or  concrete 
walls  is  called  rendering.  Before  laying  the  coarse  stuff 
the  superfluous  mortar  in  the  joints  of  brick  or  stone 
walls  should  be  cleared  off*,  as  the  mortar  used  by  brick- 
layers and  stonebuilders  often  contains  live  or  imper- 
fectly slaked  lime,  which  in  many  instances  is  the  cause 
of  the  plaster  work  blowing  or  scaling  off.  The  walls, 
whether  of  brick,  stone  or  concrete,  should  be  well  swept 
with  a  hard  coarse  broom  and  thoroughly  wetted  to  cor- 
rect the  suction,  which  otherwise  would  absorb  the  requi- 
site moisture  from  the  coarse  stuff,  causing  it  to  become 
inert  and  dry,  consequently  weak  and  non-adhesive.  In 
some  cases  the  joints  of  brick-work  should  be  raked  out 
and  the  face  of  stone  walls  roughened  by  picking.  The 
coarse  stuff  for  rendering  walls  does  not  require  so  much 
hair  or  to  be  used  so  stiff  as  fci^  coating  lathwork.  First- 
coating  ^r  reader  ing  ]s  ge^neraHy  looked  u^^on  as  a  simple 


TERMS  AND  PROCESSES 


103 


process,  but  it  should  be  carefully  laid  and  scratched,  as 
it  is  the  foundation  for  the  other  work. 

Floating, — Floating  or  second-coating,  termed  brown- 
ing," is  the  laying  of  the  second  coat  of., coarse  stuff  on 
the  first  coat  when  dry  to  form  a  straight  surface  for  the 
finishing  coat.  If  the  first  coat  has  been  standing  for 
some  time  it  should  be  well  swept  to  clear  off  any  dust 
that  may  have  accumulated  during  the  interval  between 
the  application  of  the  coats.  Where  the  coarse  stuff  is  of 
a  porous  nature  a  damp  brush  should  be  passed  lightly 
over  the  first  coat  as  the  work  proceeds  to  prevent  the 
moisture  being  sucked  out  of  the  second  layer,  which,  if 
too  dry,  would  tend  to  crack  and  fall  away.  The  coarse 
stuff  for  floating  should  be  used  in  a  softer  state  than 
for  first-coating,  because  when  too  stiff  the  extra  press- 
ure required  for  laying  is  apt  to  crack  the  first  coat  on 
lath  work.  It  also  goes  more  freely  and  firmly  into  the 
recesses  of  the  scratching.  (It  may  be  here  mentioned 
that  a  mortar  called  ^^dogga''  is  extensively  used  in 
South  Africa  for  plaster  and  building  work.  Dogga  is 
the  ground  dug  up  and  tempered  with  sand,  about  2  to 
1  for  rendering  and  floating.  Heavy  ground  requires 
more  sand.  Lime  is  very  expensive  in  that  country  and 
is  only  used  for  the  best  class  of  work.)  Floating  for 
lime  plastering  consists  of  four  parts:  (1)  Plumbing 
and  levelling  ' '  screeds ' '  to  act  as  bearing  for  the  floating 
rule  and  running  mold;  (2)  flanking  or  filling  in  the 
spaces  between  the  screeds;  (3)  scouring;  (4)  keying  the 
surface.    These  parts  are  performed  as  follows: 

Screeds.^ — In  good  work  the  wall  screeds  are  plumbed 
and  the  ceiling  screeds  levelled.  Wall  screeds  are 
plumbed  by  forming  ''dots"  at  the  top  and  bottom  of 
the  internal  and  external  wall  angles.  If  there  are  wood 
grounds  to  receive  wood  skirtings  they  are  used  instead 


CEMENTS  AND  CONCRETES 


of  bottom  dots.  The  dots  are  made  by 
driving  two  nails  through  the  first  coat 
into  the  studs  or  joints  of  the  wall, 
allowing  them  to  project  about  I/2  inch 
§Q  beyond  the  face  of  the  first  coat.  The 
position  of  the  top  nail  should  be  imme- 
I  diately  beneath  the  cornice  bracket.  If 
I  there  is  no  bracket  the  depth  of  the 
I  cornice  should  be  allowed  for.  The 
^  bottom  nail  is  placed  in  a  liije  with  the 
^  upper  member  of  the  skirting  molding, 
g  The  nails  should  be  pla(?ed  perpendicu- 
g  lar  with  each  other,  otherw^ise  the 
plumb-bobline  will  not  work  in  unison 
with  the  gauges.  The  dots  are  plumbed 
by  means  of  a  plumb-rule.  If  the  walls 
are  too  high  for  an  ordinary  sized 
plumb-rule  to  be  used  a  chalkline,  with 
a  plumb-bob  attached,  and  two  wooden 
gauges  will  be  required.  Illustration 
No.  3  shows  the  nails,  gauges  and 
plumb-bobline  in  position.  BB  are  the 
nails  in  the  wall,  one  just  below  the 
cornice  bracket  and  the  other  a  little 
above  the  floor  line;  AA  are  the  gauges 
with  the  line  hanging  fair  with  their 
shoulders,  being  the  correct  position 
>B  when  the  nails  are  plumb.  The  gauges 
are  generally  cut  out  of  a  strong  lath. 
They  must  be  made  exactly  to  the  same 
length.  The  plasterer  at  the  top  holds 
the  end  of  one  gauge  on  the  top  nail, 
with  the  chalk-line  resting  on  the  shoul- 
der of  the  gauge,  while  the  plasterer 


TERMS  AND  PROCESSES 


105 


at  the  bottom  holds  the  other  gauge  on  the  bot- 
tom nail  with  one  hand  and  guides  the  plumb-bob 
with  the  other.  The  nails  are  now  driven  in  as  re- 
quired until  they  are  plumb.  Care  must  be  taken  to 
allow  for  a  fair  thickness  for  the  floating  coat.  This 
should  not  be  more  than  %  inch  or  less  than  %  inch. 
When  working  from  a  wood  ground  the  top  dots  should 
be  kept  a  little  inside  the  plumb-line  to  allow  for  the 
traversing  of  the  cornice  screed,  because  this  screed  and 
the  gathering  at  the  bottom  of  the  cornice  are  apt  to 
throw  the  wall  out  of  plumb  unless  cut  off  or  allowed  for. 
The  dots  are  completed  by  laying  narrow  strips  of 
gauged  coarse  stuff  up  to  and  in  a  vertical  line  with  the 
top  and  bottom  nails-  the  floating  rule  is  then  applied 
and  the  stuff  worked  down  until  flush  with  the  nails.  The 
dots  should  not  be  wider  than  the  width  of  the  floating 
rule,  as  the  rule  when  bearing  on  the  nails  can  only  be 
worked  with  an  up-and-down  motion,  taking  in  only  its 
own  width.  The  length  of  the  dots  may  vary  from  5 
to  7  inches,  according  to  the  bearings  required  for  the 
cornice  and  skirting  running  mold.  Narrow  screeds  are 
easier,  quicker  and  truer  made  than  wide  screeds.  The 
latter  are  apt  to  have  a  more  or  less  wavy  surface.  This 
applies  more  especially  to  ^^laid  screeds'' — that  is 
screeds  that  are  simply  laid  and  ruled  off  without  dots 
or  other  bearings. 

Lath  dots  are  sometimes  used  instead  of  nail  dots ;  they 
are  generally  used  on  ceilings  and  lathed  partitions ;  they 
are  not  so  liable  to  crack  the  first  coat  as  nails.  They 
are  formed  by  laying  a  strip  of  coarse  stuff  and  placing 
thereon  a  straight  lath  about  6  inches  long  and  then 
applying  a  plumb-rule  or  plumb-bobline  as  described 
for  the  nail  dots.  The  lath  gives  strength  and  resist- 
ance while  working  the  floating  rule.    After  the  screeds 


106 


CEMENTS  AND  CONCRETES 


are  finished  the  laths  are  taken  out  and  the  spaces  made 
good.  Having  finished  all  the  top  and  bottom  dots,  the 
top  and  bottom  longitudinal  spaces  in  a  line  with  the 
dots,  or,  in  other  words,  the  screeds  are  laid  with  coarse 
stuff.  The  long  floating  rule  is  then  applied,  bearing  on 
the  dots  and  working  up  and  down  in  a  slanting  posi- 
tion, a  plasterer  working  the  rule  at  each  end,  and  work- 
ing together  so  as  to  keep  the  rule  square  on  edge  and 
uniformly  level.  Any  surplus  stuff  is  taken  off  the  rule 
and  applied  to  make  up  any  hollow  parts  in  the  screed 
or  returned  to  the  gauge  board,  as  the  case  may  be.  If 
the  screeds  are  extra  long  another  man  (sometimes  more) 
is  required  to  work  at  the  center  of  the  rule,  also  clean 
the  surplus  stuff  off,  and  make  up  any  deficiencies  in  the 
screed.  After  the  screeds  are  finished,  the  nails  must  be 
extracted  to  avoid  rust  discoloring  the  finishing  .coat. 
Large  surfaces  on  walls  or  ceilings  should  be  divided  in- 
to bays  by  narrow  screeds  placed  from  6  to  9  feet  apart. 
This  affords  more  freedom  and  regularity  for  laying  and 
ruling  off.  Gauged  coarse  stuff  is  sometimes  used  for 
the  main  screed,  i.  e.,  the  wall  and  ceiling  screeds  on 
which  the  cornice  is  run.  In  this  case  the  screeds  are 
finished  smooth,  or  so  that  they  only  require  a  very  thin 
or  filling-up  coat  of  gauged  putty  for  the  cornice  screeds. 
The  splayed  edges  of  screeds,  especially  gauged  screeds, 
should  be  cut  square.  A  splayed  edge  being  generally 
smooth,  affords  little  or  no  key,  and  also  being  unequal 
in  thickness,  makes  a  bad  joint  for  the  floating  coat. 
If  there  are  any  breaks  in  the  room,  the  screeds  must  be 
set  off  square  from  the  side  walls,  and  the  projections 
at  each  angle  of  the  breast  made  equal.  The  sides  are 
best  squared  with  a  large  wooden  square,  and  the  pro- 
jections regulated  with  a  gauge. 

Flanking. — Flanking  or  filling  in  consists  of  laying 


TERMS  AND  PROCESSES 


107 


the  intervening  spaces  between  the  screeds  with  coarse 
stuff,  and  then  ruling  the  surface  straight  and  flush  with 
the  screeds,  with  a  floating  rule.  Two  squads  of  men,  two 
or  three  in  each  squad,  are  required  for  this  purpose — 
one  squad  on  the  floor,  and  the  other  on  the  scaffold.  If 
the  height  of  the  room  necessitates  more  than  one  scaf- 
fold, an  additional  squad  is  required  for  each  interven- 
ing scaffold.  In  the  latter  case,  the  distance  between  the 
top  and  bottom  screeds  would  be  too  great  to  allow  a 
floating  rule  to  be  conveniently  worked.  To  overcome  this 
difficulty,  intermediate  screeds  must  be  made  at  conven- 
ient distances.  This  is  done  by  stretching  a  chalk-line 
from  the  top  to  the  bottom  screed,  and  then  forming  dots 
flush  with  the  line,  and  laying  the  screeds  as  previously 
described.  The  coarse  stuff  for  flanking  should  be  laid 
upwards,  and  in  an  angular  line.  This  plan  is  not  so  apt 
to  spring  the  lath  or  crack  the  key  at  the  deepest,  which 
is  the  thinnest  part  of  the  first  coat,  as  if  laid  across  the 
laths.  After  a  bay  is  laid,  the  surface  is  straightened 
w4th  a  floating  rule.  A  plasterer  at  the  top  and  one  at 
the  bottom  works  the  rule  together  uniformly  up  and 
down  with  a  cutting  motion,  and  keeping  it  in  a  slightly 
angular  position,  so  that  any  surplus  stuff  may  not  fall 
on  the  man  below.  A  rule  should  not  be  worked  on 
either  of  its  face  edges,  as  by  so  doing  the  face  becomes 
round  and  uneven,  and  conducive  of  unequal  screeds. 
The  filling  in  and  ruling  off  is  continued  until  all  the 
walls  are  completed.  When  elaborate  ceilings  have  to  be 
done,  involving  the  expenditure  of  much  time,  the  top 
longitudinal  screeds  are  only  formed,  and  the  floating  of 
the  walls  left  until  three  or  four  days  before  the  setting 
can  be  begun,  as  the  setting  coat  made  from  some  limes 
adheres  better  when  the  floating  coat  is  partly  green,  or 
at  least  not  bone  dry.    As  previously  mentioned,  the 


108  CEMENTS  AND  CONCRETES 


whole  process  of  preparing  lime  plaster  and  laying  it  on 
the  walls  in  thin  coats,  with  a  considerable  space  of  time 
between  the  coatings,  is  conducive  to  the  ultimate  hard- 
ness of  the  whole,  the  lime  being  first  slaked  and  then 
scoured,  all  this  time  being  exposed  to  the  carbonic  acid 
of  the  atmosphere.  Again,  each  coat  is  long  exposed  to 
the  same  influence  before  being  covered  with  the  next, 
thus  enabling  each  coat  to  harden  by  a  natural  process 
before  the  following  coat  is  laid.  All  things  being  equal, 
it  is  advisable  to  allow  each  coat  to  stand  as  long  as  pos- 
sible before  proceeding  with  the  next.  Where  the  wall 
surface  is  irregular,  causing  extra  thick  parts  in  the 
floating  coat,  the  hollow  parts  should  be  rendered  or 

dubbed  out,"  and  the  surface  scratched  before  laying 
the  floating  coat.  The  dots  for  the  ceiling  screeds  are 
formed  close  to  the  cornice  bracket.  If  there  are  no 
brackets,  the  projection  of  the  cornice  must  be  allowed 
for.  Lath  dots  are  best  for  ceiling  screeds.  They  are 
formed  at  all  the  angles,  and  made  level  all  round  the 
ceiling.  This  is  done  with  the  aid  of  a  parallel  ceiling 
rule."  When  all  the  dots  are  made,  the  screeds  are  fin- 
ished, and  the  surface  flanked  in  as  already  described. 

For  common  work,  the  wall  screeds  are  seldom 
plumbed;  but  if  there  are  breaks  in  the  room,  the  ex- 
ternal angles,  which  are  more  noticeable,  should  always 
be  plumbed.  For  this  class  of  work  two  men  generally 
work  together.  Working  from  the  floor  upwards,  one 
man  lays  a  coat  of  coarse  stuff  about  7  inches  wide,  and 
as  high  as  he  can  conveniently  reach  up  on  both  sides  of 
the  internal  angles ;  his  colleague  follows  on  with  a  float- 
ing rule  and  rules  them  straight.  Before  finishing  the 
screed,  the  rule  is  applied  on  the  portion  done,  and  grad- 
ually moved  up  until  one  end  reaches  the  cornice  line, 
to  see  if  there  Ik  a  sufficient  thickness  for  the  upper  part 


TERMS  AND  PROCESSES 


109 


of  the  screed.  The  space  between  the  first-coating  and 
the  face  of  the  rule  shows  the  thickness  available  for  the 
floating  coat.  The  desired  thickness  is  obtained  by  lay- 
ing more  stuff  on  the  screed,  or  working  it  down,  as 
the  case  may  be.  As  the  floating  rule  cannot  be  worked 
close  up  to  the  angle,  a  seam  of  coarse  stuff  is  formed  in 
the  angle. 

To  allow  for  shrinkage,  and  to  obtain  a  flrm  and 
square  angle,  the  seams  are  left  until  all  the  floating  is 
done,  after  which  they  are  cut  oft'  square  and  flush  with 
the  floating.  This  is  done  with  a  laying  trowel,  working 
it  on  its  flat  on  the  firm  floating.  Any  defects  in  the 
angles  are  made  good  when  scouring  the  float- 
ing. After  the  vertical  angle  screeds  are  firm, 
horizontal  screeds  are  laid  at  the  highest  conven- 
ient line,  and  ruled  with  a  floating  rule  bearing 
on  the  vertical  screeds.  The  intervening  spaces  are  then 
flanked*  in  by  laying  with  coarse  stuff  until  flush  with 
the  screeds.  The  surface  is  sometimes  ruled  fair  with  a 
floating  rule,  but  more  often  straightened  with  a  darby. 
After  the  scaffold  is  erected,  the  top  portions  of  the  ver- 
tical screeds  are  laid  and  ruled  with  a  floating  rule, 
working  it  so  as  to  bear  on  the  lower  part  of  the  screed 
previously  made,  which  gives  a  bearing  and  guide  for 
the  rule.  After  allowing  for  the  depth  of  the  cornice 
(if  not  bracketed),  the  top  horizontal  screed  is  then 
laid  and  ruled  with  a  floating  rule  bearing  on  the  ver- 
tical screeds.  The  intervening  spaces  are  then  filled  in 
with  coarse  stuff,  and  ruled  in  or  darbied  as  previously 
described.  The  ceiling  screeds  are  made  close  to  the  cor- 
nice bracket,  or  (if  not  bracketed)  in  a  line  with  the 
outer  member  of  the  intended  cornice.  A  screed  is  first 
made  at  each  of  the  long  sides  of  the  ceiling,  and  when 
firm  the  end  screeds  are  laid  and  ruled,  using  the  long 


ilO  CEMENTS  AND  CONCRETES 


screeds  as  bearings  for  the  floating  rule.  If  the  scaffold 
is  in  position  before  the  floating  is  commenced,  the 
vertical  screeds  should  be  formed  in  one  operation.  A 
plasterer  on  the  floor  lays  the  lower  part  of  the  screed, 
while  his  partner  on  the  scaffold  lays  the  upper  part, 
after  which  both  work  with  floating  rule  together  in 
their  respective  positions.  Where  practical  all  screeds 
should  be  finished  in  one  operation.  In  the  event  of  a 
screed  being  too  long  for  an  ordinary  sized  rule  to  take 
in  the  whole  length  and  work  it  in  one  operation,  the 
screed  can  be  made  straight  by  working  the  rule  back- 
wards and  forwards  from  end  to  end,  testing  the 
straightness  by  applying  the  rule  on  various  parts  of  the 
screed.  The  straightness  is  further  proved  by  lightly 
stretching  a  chalk-line  from  one  end  to  the  other  end 
of  the  screed.  After  the  screeds  are  firm,  the  main 
portion  of  the  ceiling  is  laid  with  coarse  stuff  flush  with 
the  screeds,  and  then  made  fair  with  a  darby. 

When  floating  large  surfaces  with  a  darby,  it  should 
be  worked  in  all  directions — longwise,  crosswise,  *  and 
diagonally  and  finishing  with  a  circular  motion.  For  or- 
dinary work  a  darby  is  an  excellent  tool  for  straighten- 
ing large  surfaces  of  floating  and  setting.  It  also  forms 
a  pleasing  and  easy  surface  on  circular  work.  For  base- 
ment and  attic  rooms  a  darby  properly  manipulated  will 
form  fairly  straight  screeds  as  well  as  the  main  surfaces. 
When  floating  large  ceiling  or  wall  surfaces  for  plain 
work,  or  where  it  is  not  necessary  that  they  should  be 
perfectly  straight,,  involving  time  and  material,  a  hol- 
low surface  is  preferable  to  a  round  surface.  A  hol- 
low surface  is  not  so  noticeable,  and  is  less  objectionable 
to  the  eye  than  a  round  surface.  It  will  be  understood 
that  a  hollow  surface,  to  be  pleasing  to  the  eye  if  noticed, 
should  flow  gradually  and  regular  from  the  screeds  to 


TERMS  AND  PROCESSES  111 


the  center  of  the  surface,  and  not  suddenly  or  in  wavy 
parts  or  patches. 

There  is  an  inferior  kind  of  floating  practiced  by 
piece-workers,  in  some  districts,  for  cottage  work,  and 
even  some  of  the  modern  jerry-built  houses.  This  is 
executed  by  floating  direct  from  the  walls  in  one  coat. 
The  surface  is  sometimes  dry-scoured  with  a  ''nail  hand 
float, ' '  water  and  proper  scouring  being  unknown  in  this 
class  of  so-called  plastering.  The  ceilings  are  simply 
laid  with  coarse  stufi:',  and  the  ridges  and  smooth  sur- 
face left  by  the  trowel  are  worked  down  and  roughened 
by  a  few  rubs  with  a  hand  float.  This  porous  and  cracked 
shell  is  finished  with  setting  stuff,  gauged  with  just  as 
much  plaster  as  will  hold  the  materials  together  for  the 
time  being.  The  minimum  of  (or  possibly  less)  trowel- 
ling is  attempted;  a  stock  brush  being  found  a  more 
easy  and  speedy  tool  than  a  trowel  for  finishing.  The 
brush  is  made  to  perform  the  trowelling  and  brushing 
off  in  one  operation.  This  shoddy  work  is  unsafe  and 
unsanitary,  and  ought  not  to  be  tolerated. 

Scouring  Coarse  Stuff. — Scouring  floated  coarse  stuff 
is  of  great  importance.  It  not  only  consolidates  and 
hardens  the  surface,  but  also  prevents  cracks  in  its  own 
body  and  the  subsequent  setting  coat.  For  these  reasons 
it  should  be  well  and  sufficiently  done.  The  straightened 
coarse  stuff  should  be  allowed  to  stand  to  permit  of 
shrinkage,  evaporation  of  surface  moisture,  and  a  firm 
surface  before  proceeding  with  the  scouring.  Working 
a  hand  float  on  a  soft  surface  tends  to  form  "water 
blubs''  and  hollow  parts.  When  the  surface  is  firm, 
but  not  dry,  the  work  is  fit  to  scour.  This  is  done  by 
the  plasterer  having  a  hand  float  in  one  hand,  and  a 
stock  brush  in  the  other,  with  which  he  sprinkles  water 
on  the  surface,  and  vigorously  applies  the  float  with  a' 


112  CEMENTS  AND  CONCRETES 


rapid  circular  motion,  using  a  little  soft  stuff  to  fill  up 
any  small  holes  or  inequalities  that  may  have  been  left 
after  the  floating  rule.  Care  must  be  taken  that  no  part 
is  missed  or  less  scoured  and  that  the  whole  surface  is 
thoroughly  and  uniformly  scoured.  The  floating  should 
be  scoured  twice,  or  for  best  work  three  times,  and  allow- 
ing the  work  to  stand  from  three  to  five  hours,  accord- 
ing to  the  state  of  the  atmosphere,  between  the  first  and 
second  scouring,  and  one  day  between  the  second  and 
third  scouring.  The  final  scouring  should  be  continued 
until  there  is  little  or  no  moisture  left  on  the  surface. 
To  obtain  the  same  strength  and  solidity,  all  other  things 
being  equal,  coarse  stuff  composed  with  a  weak  lime  or 
containing  inferior  or  an  excess  of  sand,  or  having  in- 
sufficient hair,  or  sparsely  tempered  and  used  in  an 
over-soft  condition,  requires  a  greater  amount  of  scour- 
ing than  coarse  stuff  which  is  composed  with  a  strong 
lime,  or  containing  good  sand  and  in  due  proportion,  or 
with  an  ample  quantity  of  hair,  or  well  tempered,  and 
used  in  a  moderately  stiff  yet  plastic  condition.  Even 
with  extra  scouring  the  ultimate  strength  of  inferior 
coarse  stuff  is  remote  and  doubtful.  This  simple  mat- 
ter is  a  witness  to  the  fact  that  inferior  or  insufficient 
materials  require  more  labor  than  good  and  sufficient 
materials  and  that  the  results  are  somewhat  vague  and 
often  unsatisfactory. 

Keying, — All  plastic  materials  have  great  adhesive 
powers,  especially  to  each  other.  Yet  when  laying  a  thin 
body  of  fine  material  on  a  coarse  material  which  has  a 
more  or  less  smooth,  dry  and  absorptive  surface,  such  as 
laying  setting  stuff  on  floated  coarse  stuff,  the  adhesion 
is  partly  nullified.  Portland  cement  or  hydraulic  limes, 
w^hich  set  nearly  as  soon  as  laid,  require  no  scouring,  and 
being  left  from  the  floating  rule  with  an  open  grained  or 


TERMS  AND  PROC'eSSES 


113 


rough  surface,  a  natural  key  is  obtained  for  the  final 
coat;  but  coarse  stuff,  which  only  sets  or  becomes  hard 
by  evaporation  of  its  moisture,  must  be  scoured  to  con- 
solidate the  yielding  and  soft  body.  Scouring  leaves  a 
close-grained  and  somewhat  smooth  surface,  offering  lit- 
tle or  no  key  to  the  setting  coat.  The  floated  coat  being 
often  dry  before  the  setting  coat  is  applied,  the  suction 
varies  greatly;  sometimes  it  is  regular,  at  other  times  it 
occurs  in  patches.  Sometimes  the  suction  is  so  excess- 
ive that  the  setting  stuff  dries  up  and  peels  as  soon  as 
laid,  and  in  other  instances  the  reverse  occurs,  there 
being  no  suction  at  all.  In  the  latter  case  the  setting 
stuff  runs  downwards  in  the  form  of  globules  or  in  rivu- 
lets. These  defects  may  to  a  certain  extent  be  corrected 
by  laying  the  setting  stuff  while  the  floating  is  still 
green,  or  by  saturating  the  surface  if  the  floating  is  dry. 
Yet  to  obtain  permanent  cohesion  in  the  two  coats  it  is 
necessary  to  key  or  roughen  the  surface.  This  is  best 
done  by  brushing  the  surface  as  soon  as  scoured  with  a 
stiff  whalebone  broom  or  with  a  wire  brush.  A  common 
plan  is  to  dry  scour  with  a  ^^nail  float'' — i.,.e.,  a  hand 
float  with  the  point  of  a  nail  projecting  about  Yg  inch 
beyond  the  sole  of  the  float.  When  this  method  is  em- 
ployed the  float  should  be  worked  in  a  close  circular 
motion  so  as  to  leave  a  series  of  close  and  irregular  in- 
dents. The  usual  and  careless  way  of  working  the  float 
in  a  wide  circular  motion  leaves  the  indents  too  wide 
apart  to  give  a  sound  and  uniform  key:  indeed,  this 
method  is  of  little  service.  A  new  tool  for  keying  coarse 
stuff  has  been  recently  introduced,  which  is  called  a 
''devir'  and  is  similar  to  the  nail  float,  with  the  excep- 
tion that  there  are  four  nail  points  projecting  on  the 
sole,  one  of  which  is  placed  about  1^2  inches  from  each 
angle.    The  process  of  keying  the  coarse  stuff  with  this 


114  CEMENTS  AND  CONCRETES 


is  termed  "devilling/'  The  work  is  more  speedily  and 
better  done  with  the  ''devil"  than  with  the  nail  float. 

After  the  floating  is  flnished  the  next  part  of  interior 
plaster  work  is  the  running  of  the  cornice,  and  then  fin- 
ishing the  ceiling  and  walls;  but  in  order  to  continue 
the  methods  of  setting,  the  running  of  the  cornice,  etc., 
are  described  in  subsequent  pages,  and  the  setting  and 
other  parts  of  wall  work  are  first  described  as  follows : 

Setting, — Setting  is  the  laying  and  finishing  the  final 
coat  on  fioating,  termed  ''finishing,"  and  "hard  finish" 
or  "putty  coat."  In  the  best  w^ork  great  skill  and  care 
is  required  to  make  the  surfaces  perfectly  true  and  uni~ 
form  in  color,  smoothness  and  hardness.  The  material 
for  three-coat  work  is  generally  known  as  "setting 
stuff."  The  mode  of  making  has  already  been  de- 
Scribed.  Setting  stuff  should  not  be  applied  until  the 
floating  is  quite  firm  and  nearly  dry,  to  allow  for  any 
contraction  that  may  take  place  in  the  floating.  If  the 
floating  should  become  quite  dry  during  the  time  re- 
quired for  cornice  and  ceiling  work,  or  where  subjected 
to  strong  winds  or  a  warm  atmosphere,  it  should  be  well 
wetted  a  day  or  two  before  the  setting  coat  is  com- 
menced. This  prevents  the  too  rapid  absorption  of  mois* 
ture  from  the  setting  coat  and  gives  a  closer  union  of 
the  floating  and  setting  coats.  Before  wetting  copi- 
ously, a  small  portion  of  the  floating  should  be  tested 
with  a  wet  brush  to  ascertain  the  degree  of  suction.  In 
some  floating  there  is  no  suction,  or  at  least  there  is 
none  until  the  surface  has  been  dampened  and  the  glaze 
and  sometimes  grease  has  been  washed  off.  Glaze  is 
caused  by  slightly  hydraulic  lime,  also  by  insufficient 
scouring.  Glaze  is  more  noticeable  on  first-coating 
which  has  been  left  smooth  by  the  laying  trowel.  Grease 
occurs  through  friction,  also  dirt  where  the  float  is  left 


TERMS  AND  PROCESSES  115 


long  exposed.  These  matters  of  excessive  and  non- 
suction,  dry,  glazed  or  greasy  surface,  either  singly  or 
in  combination,  also  smooth  or  unkeyed  floating,  are  the 
cause  of  cracked  or  scaly  setting,  which  one  sees  more  or 
less  in  a  plaster  career.  It  is  therefore  absolutely  neces- 
sary, to  insure  perfect  cohesion  of  the  two  coats,  that 
the  floated  surface  should  be  uniformly  keyed,  clean  and 
damp  before  the  setting  coat  is  layed.  Setting  consists 
of  laying  the  stuff,  scouring,  trowelling  and  brushing  the 
surface. 

Laying  Setting  Stuffs — The  setting  stuff  is  laid  in  two 
coats,  the  second  following  immediately  upon  the  first. 
The  laying  is  best  done  with  a  skimming  float,  which 
leaves  the  face  of  the  first  coat  rougher  to  receive  the 
second  than  if  done  by  a  laying  trowel,  which  leaves  it 
smooth.  The  second  coat  should  also  be  laid  with  a 
skimming  float,  which  leaves  a  more  open  grain  for  the 
purpose  of  scouring.  When  laying  setting  stuff  some 
men  take  a  trowelful  or  skimming-floatful  off  the  hawk 
and  stoop  to  spread  the  stuff  from  bottom  to  top  with 
an  upward  motion,  laying  the  joint  with  a  return  down- 
ward motion;  but  a  smart  man  can  take  a  trowelful  or 
floatful  of  stuff  and  spread  it  with  a  downward  motion 
from  top  to  bottom  and  lay  the  joint  with  the  return  mo- 
tion, this  saving  one  stoop  in  each  spread  or  floatful. 
This  is  similar  to  laying  setting  stuff  on  a  ceiling.  A 
man  who  has  a  thorough  command  of  the  trowel  hand 
always  lays  the  stuff  in  a  long  even  spread  outward, 
and  lays  the  joint  with  the  inward  return  motion.  After 
one  side  of  a  bay  or  wall  is  laid  the  surface  is  then 
scoured,  trowelled  and  brushed. 

Scouring  Setting  Stuff. — The  importance  of  good  and 
sufficient  scouring  of  setting  stuff  with  water  cannot  be 
too  strongly  insisted  upon.    The  scouring  and  the  water 


116  CEMENTS  AND  CONCRETES 


combined  consolidate,  harden  and  render  the  surface  of 
a  uniform  texture  and  evenness.  The  work  must  be  well 
and  thoroughly  scoured,  twice  with  water  and  an  ordi- 
nary hand  float  and  finally  with  a  cross-grained  float. 
The  hand  float  is  worked  with  a  short  and  rapid  circular 
motion  and  sprinkling  water  uniformly  with  a  stock 
brush  until  the  surface  is  uniform  in  moisture  and  tex- 
ture. After  a  rest  to  allow  the  stuff  to  shrink  the  scouring 
is  repeated,  and  then  it  is  ready  for  the  final  scouring. 
This  is  best  done  with  a  cross-grained  hand  float,  which, 
having  sharp  square  edges,  cuts  off  all  ridges  and  leaves 
the  setting  with  a  uniform  and  even  surface  that  cannot 
be  so  quickly  or  as  well  done  with  an  ordinary  hand  float. 
Water  is  more  sparingly  used  for  the  final  scouring, 
using  only  as  much  as  will  moisten  the  surface  and  allow 
the  float  to  work  freely.  The  scouring  is  continued  until 
a  dense,  even  and  close-grained  surface  is  obtained  for 
the  trowelling. 

Trowelling  and  Bintshing  Setting  Stuff. — Trowelling 
setting  stuff  is  best  done  by  the  use  of  a  half  worn 
trowel  (commonly  called  a  polisher''),  the  edges  of 
which  should  be  perfectly  straight  and  parallel.  Some 
men  use  an  old  and  worn  trowel  with  the  point  narrower 
than  the  heel.  This  shaped  trowel  should  never  be  used 
for  high  class  work,  since,  not  being  parallel,  the  press- 
ure when  trowelling  is  not  equal,  and  the  heel  or  widest 
part  is  apt  to  score  the  surface  of  the  setting.  The 
trowel  and  water  should  be  perfectly  clean  to  prevent 
any  discoloration.  The  trowelling  should  loe  done  by 
one  man  following  up  the  other,  who  is  finishing  the  final 
scouring.  This  is  done  by  the  plasterer  having  a  polish- 
ing trowel  in  one  hand  and  a  stock  brush  in  the  other, 
with  which  he  sprinkles  water  on  the  surface  and  works 
the  trowel  in  long  and  vigorous  strokes,  first  downwards 


TERMS  AND  PROCESSES  117 


and  upwards,  and  then  crossways  or  diagonally.  This  is 
repeated,  using  the  water  more  sparingly  and  finishing 
or  ''trowelling  off  with  an  up-and-down  motion  and 
leaving  the  surface  free  from  "fat"  or  ''glut.'^  The 
work  is  then  brushed  with  a  wet  stock  brush,  first  up  and 
down,  then  crossways,  afterwards  up  and  down  a  sec- 
ond time.  The  brush  is  then  semi-dried  by  violent  shak- 
ing, or  rubbing  on  a  clean  board,  the  work  again  being 
brushed  as  before  and  finished  perpendicular. 

General  Remarks  on  Setting. — When  the  work  is  re- 
quired for  painting  the  setting  stuff  is  laid  on  the  form 
of  screeds,  and  when  firm  the  intervening  spaces  are 
laid  flush  with  the  screeds  atid  the  whole  surface  ruled 
fair  with  a  floating  rule.  Should  there  be  any  hollow 
or  soft  places  (the  latter  being  liable  to  shrink),  they  are 
filled  in  with  more  setting  stuff  and  ruled  over  again. 
This  is  repeated  until  the  whole  surface  is  true  and  uni- 
form in  thickness  and  firmness.  The  whole  surface  can 
be  scoured,  trowelled  and  brushed  in  one  operation. 
This  method  has  the  advantage  of  saving  joints  at  the 
connections  between  the  height  a  man  can  lay  and  finish 
the  setting  stuff. 

Joints,  unless  carefully  done,  are  an  eyesore,  as  they 
are  liable  to  be  more  or  less  discolored  and  uneven  on 
the  surface.  The  best  method  for  making  joints  and 
setting  stuff,  where  it  is  inconvenient  to  lay  and  finish 
the  whole  surface  in  one  operation,  is  to  leave  the  edge 
of  the  joint  untrowelled,  leaving  a  scoured  margin  so 
that  the  adjoining  portion  can  be  laid  and  scoured  with- 
out spoiling  the  trowelling  of  the  first  portion.  For  in- 
stance, when  setting  the  walls  of  a  room  one  scaffold 
high  the  top  parts  are  laid  down  to  the  level  of  the 
scaffold,  or  as  far  as  convenient,  and  the  surface  scoured 
and  trowelled.    The  latter  must  not  extend  to  the  end 


118  CEMENTS  AND  CONCRETES 


of  the  scoured  part,  so  as  to  leave  an  untrowelled  margin 
about  4  or  5  inches  wide  until  the  scaffold  is  struck. 
After  the  scaffold  is  removed  the  lower  portions  of  the 
walls  are  laid  flush  with  the  untrowelled  margin,  and 
then  the  surface  is  scoured  as  before,  always  going  well 
over  the  joint.  The  surface  is  then  finally  scoured  with 
a  cross-grained  float,  taking  care  to  moisten  and  rescour 
the  untrowelled  margin  to  render  the  whole  of  the 
scoured  surface  equal  in  texture  and  moisture  for  trowel- 
ling. The  surface  is  then  trowelled  and  brushed  as  al- 
ready described,  taking  care  to  go  over  the  trowelled  and 
brushed  joint.  By  this  method  no  joints  are  visible,  and 
an  even  surface  is  obtained.  When  the  suction  is  slow 
or  irregular,  causing  the  setting  stuff  to  run  or  be  soft 
in  places,  float  the  surface  with  a  darby  until  sufficiently 
fair  and  firm  to  be  scoured.  A  darb}'  is  very  useful  for 
forming  a  fair  surface  on  setting  stuff  before  scouring 
and  trowelling.  It  forms  the  next  best  surface  to  a 
ruled  surface.  A  darbied  surface  is  better  and  truer 
than  a  laid  surface. 

No  more  setting  stuff  should  be  laid  than  can  be  con- 
veniently finished  in  one  operation  or  day.  Where  prac- 
tical, one  side  of  a  wall  should  be  finished  in  one  piece, 
and  sufficient  men  should  be  employed  thereon.  If  the 
room  is  not  too  high,  one  man  or  set  of  men  may  do  the 
upper  part,  while  another  man  or  set  of  men  does  the 
lower  part.  The  joints  are  then  made  while  the  setting 
stuff  is  green.  In  high  rooms,  several  sets  of  men  work 
together  on  different  scaffolds,  each  about  6  ft.  2  in. 
apart.  All  angles  should  be  ruled  in  with  a  long  float- 
ing rule.  External  angles  are  sometimes  formed  by 
nailing  a  running  rule  or  a  straight  edged  plumb  on  one 
side  of  the  wall,  to  act  as  a  guide,  but  external  angles  are 
generally  finished  with  a  run  cement  bead  or  an  arris. 


TERMS  AND  PROCESSES  Il9 


An  average  thickness  of  %  inch  of  setting  coat  when 
finished  gives  the  best  result.  It  should  not  exceed  3-16 
inch,  or  be  less  than  1-16  inch  in  thickness.  If  too  thick, 
it  is  liable  to  crack  and  flake;  if  too  thin,  it  is  liable  to 
peel.  Where  extra  strength,  and  cohesion  between  the 
floating  and  setting  coats  is  desirable,  the  first  coat  of  the 
setting  has  a  little  white  hair  mixed  with  it.  White  hair 
does  not  show  through  the  last  coat. 

Common  Setting. — Common  setting  for  wall  and  ceil- 
ings is  generally  used  for  second-class  work.  It  is  done 
by  laying  one  coat  of  setting  stuff  with  a  skimming  float, 
and  scouring  and  trowelling  once  and  brushing  twice. 
Where  the  floating  cracks  by  contraction,  or  by  using  in- 
sufficient hair  in  the  coarse  stuff,  or  by  w^ant  of  scouring, 
or  where  the  work  is  green,  the  cracks  are  knocked  in 
with  a  hammer.  The  indents  are  then  filled  up  with 
gauged  setting  stuff,  and  the  whole  surface  laid  with  a 
coat  of  this  material,  on  which  a  coat  of  neat  setting  stuff 
is  laid,  scoured,  trowelled,  and  brushed  in  the  usual 
way. 

Skimming. — Skimming  is  an  inferior  class  of  setting, 
and  is  only  used  for  the  most  common  work.  It  is  done 
by  laying  a  coat  of  fast-setting  stuff  with  a  laying  trowel. 
The  stuff  is  skimmed  over  the  floating  as  thin  as  possible, 
using  only  as  much  stuff  as  will  whiten  and  smooth  the 
floating  surface.  It  is  trowelled  once,  and  brushed  as 
soon  as  laid. 

Colored  Setting. — A  beautiful  color  and  brilliant  finish 
for  walls  is  obtained  by  mixing  an  equal  quantity  of 
sifted  marble  dust  with  setting  stuff  and  using  this 

marble  setting  stuff"  as  a  final  coat.  Ordinary  setting 
stuff  is  greatly  improved  by  substituting  a  part  of  mar- 
ble, or  alabaster,  or  gypsum  dust,  equal  in  bulk  to  half 
the  sand  generally  used.    The  marble  dust  should  be  as 


120  CEMENTS  AND  CONCRETES 


coarse  as  the  sand.  Crushed  spar  is  sometimes  used  in 
setting  stuff  to  obtain  a  sparkling  surface.  Barytes,  sco- 
ria, and  slag  are  sometimes  used  as  a  substitute  for  sand, 
for  coloring  and  hardening  purposes.  Brick  dust  is  also 
used  for  coloring,  and  weather  and  heat  resisting  pur- 
poses. Ground  glass  as  used  by  Indian  plasterers  gives 
a  sparkling  surface.  Setting  stuff  may  also  be  colored 
with  the  same  materials  as  described  for  colored  stucco. 
Where  marble  dust  or  any  of  the  above  materials  are 
used,  they  should  not  be  added  until  the  setting  stuff  is 
required  for  immediate  use.  They  should  not  be  used 
until  perfect  amalgamation  has  ensued. 

Gauged  Setting. — Gauged  setting  is  used  where  the 
floating  is  soft,  or  where  the  work  is  required  for  imme-' 
diate  use,  and  also  for  finishing  gauged  floating.  This 
is  performed  by  one  man  laying  the  gauged  stuff  with 
a  skimming  float,  while  his  partner  follows  up  with  a 
darby  to  lay  the  surface  fair.  Another  batch  of  setting 
stuff  is  then  gauged,  and  one  man  lays  a  thin  coat  with 
a  trowel,  and  the  other  man  follows  immediately  and 
.trowels  the  work  before  it  is  set.  The  surface  is  finished 
by  brushing  with  a  semi-wet  brush.  Gauged  setting 
should  never  be  scoured  unless  the  size  water  is  used  in 
the  gauge  to  delay  the  setting,  as  it  will  kill  the  plaster 
and  render  the  stuff  useless.  Even  if  size  water  is  used, 
the  scouring  must  be  slightly  and  quickly  done.  If  a 
gauged  surface  is  desirable,  a  fair  and  hard  surface  is 
obtained  by  simply  darbying  and  trowelling  as  soon  as 
laid. 

Gauged  Putty  8et.\ — Ceilings  are  sometimes  set  with 
gauged  putty.  This  is  best  done  by  first  laying  a 
''scratch  coat'^  of  gauged  putty  with  a  skimming  float, 
and  then  passing  a  hand  float  over  the  surface  (before 
the  stuff  is  set)  to  lay  down  any  ridges,  and  make  the 


TERMS  AND  PROCESSES 


121 


surface  more  even  to  receive  the  second  coat.  This  is 
laid  with  a  laying  trowel,  and  then  trowelled  before  the 
stuff  is  set.  The  surface  is  then  finished  with  a  semi-wet 
brush.  Trowelling  after  the  stuff  is  set,  or  even  has 
begun  to  set,  kills  the  stuff,  and  causes  it  to  peel.  A 
little  washed  sand  added  to  the  putty  makes  a  stronger 
surface,  and  not  so  apt  to  peel. 

Putty  Set. — In  some  districts  common  ceilings  are  fin- 
ished with  a  thin  coat  of  neat  lime  putty ;  but  unless  the 
putty  is  made  from  grey  limestone,  or  is  of  a  hydraulic 
nature,  the  work  is  more  or  less  we^k,  and  in  most  cases 
practically  useless. 

hiternal  Angles. — The  setting  coat  of  internal  angles 
on  room  walls  should  be  ruled  fair  and  then  cleaned  out 
with  a  feather-edged  rule.  Before  scouring  the  setting 
stuff,  the  angles  should  be  squared  and  made  straight 
with  an  angle  float.  The  angle  float  is  a  tool  now  unfor- 
tunately seldom  used,  but  it  is  the  best  tool  for  making 
a  true  angle.  In  the  absence  of  an  angle  float,  the  angle 
should  be  made  fair  and  square,  with  a  cross-grained 
float,  and  finished  with  a  margin  trowel  or  the  heel  of  a 
laying  trowel.  The  common  way,  used  in  some  districts, 
of  finishing  an  angle  with  a  gauging  or  pointed  trowel, 
should  not  be  encouraged,  as  it  is  impossible  to  make  a 
true  angle  with  a  tool  of  this  shape. 

External  Angles. — The  external  angles  of  room  walls 
and  windows  are  generally  finished  with  a  bead,  but  in 
some  instances  with  a  plain  arris,  splay,  or  small  mould- 
ing. They  are  formed  with  Parian  or  other  white 
cement,  and  usually  run  after  the  floating  is  done.  The 
floating  should  be  cut  square  on  each  side,  and  down  to 
the  brick  or  lath  work.  After  dusting  and  wetting  the 
foundation,  a  running  rule  is  fixed  on  one  side,  and  then 
the  bead  or  arris  is  run.    The  run  edges  form  bearings 


J 22  CEMENTS  AND  CONCRETES 


lor  the  setting  coat.  A  run  arris  is  more  speedily  done 
and  truer  than  a  ruled  and  trowelled  arris.  In  some 
districts  wooden  beads  are  used  for  external  angles.  The 
floating  is  cut  down  at  each  side  of  the  bead,  to  allow  the 
quirks  to  be  formed  when  the  setting  coat  is  laid.  When 
the  setting  coat  is  trowelled,  the  quirks  are  formed  by 
applying  a  large-headed  nail  on  the  bead,  and  drawing 
it  up  and  down  to  cut  the  stuff  out.  They  are  then  fin- 
ished by  working  a  laying  trowel  up  and  down  until 
smooth  and  true,  and  afterwards  wet-brushed.  The 
bead  quirks  are  sometimes  cut  out  by  aid  of  a  wooden 
template,  also  by  laying  a  straight  edge  on  the  work  as 
a  guide  for  cutting  the  stuff  out.  They  are  then  finished 
with  a  trowel  and  brush,  as  already  described. 

Skirtings, — Skirtings  or  base,  are  sometimes  formed 
in  wood,  but  are  often  formed  in  cement.  Cement  skirt- 
ings are  far  more  sanitary  than  wood  skirtings,  as  the 
former  connects  the  wall  and  the  floor  in  one  solid  fire- 
resisting  and  vermin-proof  body,  whereas  wood  skirtings, 
owing  to  their  nature  and  construction,  afford  a  ready 
harbor  for  vermin,  and  offer  but  little  or  no  resistance 
to  damp  and  fire — indeed,  their  hollow  formation  pre- 
sents a  vent  in  the  case  of  fire.  Parian  or  other  white 
cement  is  generally  used  where  a  fine  finish  is  desirable, 
and  Portland  cement  where  the  work  is  exposed  to  wet 
and  hard  wear.  Skirtings  are  generally  run  by  first 
roughing  out  the  plinth  by  aid  of  a  gauge  rule  bearing 
on  the  floating,  and  then  forming  a  running  screed,  and 
fixing  a  running  rule  on  the  plinth.  The  skirting  mould- 
ing is  then  run  in  the  usual  way,  after  which  the  running 
rules  are  taken  off,  and  the  plinth  set.  The  mould  plate 
should  be  cut  to  form  about  1  inch  of  the  top  part  of  the 
plinth,  to  form  the  arris,  and  a  bearing  when  setting  the 
plinth.     The  annexed  illustration  (No.  4)  shows  the 


TERMS  AND  PROCESSES 


123 


method  of  forming  the  core  and  plinth,  and  running 
the  moulding.  Fig.  1  shows  the  gauge  rule  (G)  in  posi- 
tion to  form  the  core  (C).  The  gauge  rule  is  from  3 
feet  to  4  feet  in  length.  The  plinth  is  formed  by  first 
roughing  out  with  gauged  stuff,  and  then  drawing  the 
gauge  rule  along  the  floating  to  form  the  core,  and  a 
fair  surface  for  the  running  screed.  Fig.  2  shows  a  sec- 
tion to  form  the  core  (C).  The  gauge  rule  is  from  3 
(R)  fixed  on  the  plinth  or  core  (C). 


TwO'Coat  Work. — This  is  a  cheap  method  of  plaster- 
ing, and  only  used  for  common  work,  such  as  the  walls 
of  factories,  warehouses,  &c.  It  is  performed  by  laying 
one  coat  of  coarse  stuff  and  then  forming  the  surface 
fair  with  a  darby,  after  which  it  is  scoured  once.  It  is 
then  finished  by  laying  a  thin  coat  of  setting  stuff  over 
the  surface,  and  then  trowelling  once  and  brushing  twice 
wet  and  once  semi-wet. 

One-and-a-Half-Coat  Work, — This  is  sometimes  termed 
' ' coat-and-half  work."  It  is  a  species  of  two-coat  work 
—in  fact^  it  is  so  termed  in  some  districts.  It  is  done  by 


rSKiRtiNG  Formation* 


NO.  4. 


124  CEMENTS  AND  CONCRETES 


first  laying  a  coat  of  coarse  stuf?  fair,  and  then  scratch- 
ing the  surface  with  a  coarse  broom,  after  which  a  thin 
coat  of  extra  fat  coarse  stuff  is  laid,  straightened  with  a 
darby,  and  then  trowelled  and  brushed.  The  second  coat 
must  be  laid  while  the  first  is  green.  This  permits  the 
two  coats  to  amalgamate  better,  and  the  surface  to  be 
more  easily  worked  and  finished. 

Stucco. — Stucco  is  an  Italian  term  usually  applied  in 
Italy  to  a  superior  species  of  external  plastering.  Ac- 
cording to  Vasari,  Primaticcio  ^'did  the  first  stucchi  ever 
executed  in  France,  and  also  the  first  frescos."  In  the 
United  States  stucco  is  a  somewhat  indefinite  term,  used 
loosely  for  various  plastic  mixtures  in  whose  composi- 
tion lime,  plaster,  or  cements  enter.  Hydraulic  lime 
was  formerly  used  for  external  stucco.  Roman  cement 
was  extensively  used  for  stucco  fronts  during  the  first 
half  of  the  present  century.  Selenitic  lime  has  some- 
times been  used  for  a  similar  purpose.  These  materials 
are  now  entirely  superseded  by  Portland  cement.  The 
adoption  in  England  of  stucco  externally  to  give  brick 
houses  the  appearance  of  stone  is  due  to  Robert  Adam. 
Its  plastic  nature  enables  it  to  adapt  itself  to  most  archi- 
tectural purposes  with  very  considerable  decorative  ef- 
fects. The  more  general  use  of  stone  and  the  improve- 
ments in  terra  cotta  have  so  greatly  decreased  the  use  of 
stucco  for  fronts,  that  stucco  has  become  a  synonym  for 
a  sham,  and  its  real  usefulness  for  certain  works  and 
places  has  been  greatly  overlooked.  When  properly  pre- 
pared and  manipulated  it  makes  excellent  work,  and  in 
the  near  future  a  large  use  may  be  predicted  for  its  use. 

Old  Stucco. — It  has  already  been  shown  that  stucco 
was  largely  employed  by  the  ancients  for  plain  and  dec- 
orative purposes.  The  temple  of  Apollo  at  Delos,  and 
even  the  first  Parthenon  under  the  ^gis  of  Pallas  her- 


TERMS  AND  PROCESSES  125 


self,  were  plastered  with  stucco.  Vitruvius  in  his  sev- 
enth book  mentions  stucco  under  the  name  of  opus  al- 
larium,  sometimes  written  album  opus.  Tectorium  opus 
(from  tector,  a  plasterer)  was  a  name  given  by  the  Ro- 
mans to  a  mortar  used  for  plastering.  According  to 
Vitruvius,  Palladius,  and  Pliny,  there  seems  to  have  been 
a  difference  between  tectorium  opus  and  that  called  al- 
barium  or  album  opus.  Vitruvius  says  tectorium  was 
composed  of  three  coats  of  lime  and  sand,  and  three  of 
lime  and  marble.  According  to  Winckelman,  the  united 
thickness  of  these  coats  was  not  more  than  one  inch. 
The  first  coat  was  of  common,  but  old,  lime  and  sand, 
and  when  it  was  nearly  dry  a  second  coat  of  lime  was 
laid,  and  on  this  drying  a  third  coat  of  fine  lime  was  laid 
and  made  fair.  The  work  was  then  laid  with  another 
two  coats  of  lime  and  marble,  and  finished  with  a  coat 
of  fine  marble  powder.  The  marble  mortar  was  fre- 
quently beaten  to  render  it  tough  and  yet  plastic,  and 
it  was  judged  fit  for  use  when  it  would  no  longer  stick 
to  the  trowel.  When  the  lime  mortar  was  dry,  the  mar- 
ble mortar  was  laid,  each  successive  coat  of  marble  mor- 
tar being  laid  before  the  preceding  one  was  quite  dry. 
The  first  coat  of  marble  mortar  was  composed  of  coarse 
ground  marble  and  old  lime,  the  second  of  fine  ground 
marble  and  lime,  the  finishing  coat  being  neat  marble 
ground  to  a  fine  powder,  and  laid  before^the  second  coat 
was  dry,  and  worked  with  a  wood  float  until  the  surface 
was  consolidated  and  straight.  When  dry  it  was  pol- 
ished with  lime  and  chalk  or  with  marble  until  like  mar- 
ble itself.  Old  stucco  has  been  found  so  hard  and  highly 
polished  that  it  has  been  used  for  looking-glasses  and 
tables.  In  time  it  became  hard  and  not  liable  to  crack, 
and  formed  an  excellent  ground  for  the  painting  with 
which  the  Greeks  and  Romans  decorated  the  walls  of 


126  CEMENTS  AND  CONCRETES 


their  houses.  According  to  Vitruvins,  this  painted  plas- 
ter could  be  detached  without  fear  of  injury,  and  de- 
tached slabs  were  carried  to  Italy  and  inserted  in  the 
walls  of  Roman  houses.  To  prevent  the  cracking  of  the 
work  done  on  wood,  it  was  strengthened  by  two  layers 
of  reeds,  one  layer  crossing  the  other  at  right  angles. 
To  insure  dryness,  and  allow  the  plaster  to  attain  its 
proper  hardness,  the  walls  were  perforated  at  suitable 
places.  The  tectorium  was  then  decorated  with  brilliant 
colors,  which  were  applied  on  the  last  coat  while  it  was 
fresh;  and  to  heighten  the  brilliancy  and  endurance  of 
the  colors  the  surface  was  rubbed  over  vv^ith  wax  and 
pure  oil.  When  marble  was  used  with  lime  in  place  of 
sand  it  was  termed  martmoratum.  The  alburium  or 
album  opus  was  what  we  term  plaster  or  stucco.  The 
Greeks  named  tectorium  and  alburium,  koniama  and 
kalachrisis. 

Slabs  of  tectorium  from  the  walls  of  Pompeii  and  Her- 
culaneum  are  now  in  the  Museum  of  Portici,  and  speci- 
mens are  also  in  the  South  Kensington  Museum.  In  the 
Museum  of  Practical  Geology,  London,  there  are  several 
pieces  of  old  plaster,  taken  from  the  ruins  of  Pompeii, 
some  of  which  show  that  the  decorative  colors  were  not 
applied  a  la  fresco,  but  subsequent  to  the  polishing. 
Stucco  and  plaster  are  really  two  very  different  things. 
Stucco  has  for  its  base  carbonate  of  lime,  generally  burnt 
limestone  or  chalk,  with  which  putty- lime  and  coarse 
stuff  is  mixed  with  sand,  &c.^  and  used  for  plastering 
walls  and  ceilings.  Plaster  has  for  its  base  sulphate  of 
lime,  being  made  from  gypsum,  and  is  used  for  cast 
w^ork  and  gauging  with  lime  putty,  &c.  The  best  kinds 
of  stucco  will  resist  the  action  of  weather,  and  can  be 
washed.  Plaster,  unless  specially  prepared  or  indurated, 
perishes  by  exposure,  at  least  in  our  climate,  and  cannot 


TERMS  AND  PROCESSES 


127 


be  washed.  Stucco  is  a  superior  kind  of  mortar,  and  it 
may  be  used  for  plastering  or  for  modelling.  The  ad- 
mixture of  various  materials  with  lime  and  with  plaster 
to  form  stucco  is  referred  to  by  many  ancient  writers. 
Pliny  mentions  fig  juice  as  being  mixed  with  stucco. 
The  Egyptians  mixed  mud  from  the  Nile  with  plaster 
for  some  of  their  work.  Elm  bark  and  hot  barley  water 
was  mixed  with  the  stucco  for  Justinian's  Church  of  the 
Baptist,  Constantinople.  We  find  bullocks'  blood  em- 
ployed for  this  purpose  as  well  in  mortar  for  Rochester 
Cathedral  in  the  latter  part  of  the  ninth  century.  Bishop 
Gundulph  (1077-1108)  is  stated  to  have  mixed  blood 
with  lime  to  make  it  hard.  Hot  wax  mixed  with  lime 
was  used  at  Rockingham  Castle  in  1280.  White  of  eggs 
and  strong  wort  of  salt  were  mixed  with  lime  used  for 
Queen  Eleanor's  Cross  at  Charing  Cross  in  1300.  Pitch 
and  wax  were  mixed  with  the  lime  used  for  Edward 
II. 's  works  at  Westminster  in  1324.  Mediaeval  build- 
ers habitually  used  beer,  eggs,  milk,  sugar,  gluten,  &c., 
for  mixing  with  mortar  for  cathedrals.  Frequent  en- 
tries found  in  the  archives  prove  this.  One  reads,  *^For 
beer  to  mix  with  the  mortar. ' '  Bess  of  Hardwicke 's  ma- 
sons used  beer  in  their  mortar,  having  to  melt  it  in  the 
cold  winter  of  her  death.  Old  plaster  is  found  to  have 
rye  straw  mixed  with  it  for  binding,  and  was  very  strong. 
A  brown  substance  somewhat  like  plaster,  but  full  of 
fibre,  was  in  use  in  the  sixteenth  century.  The  accounts 
for  the  repairs  of  the  steeple  of  Newark  Church  in  1571 
contain  an  entry,  ^'6  strike  of  malt  to  make  mortar  to 
blend  with  ye  lyme  and  temper  the  same,  and  350  eggs 
to  mix  with  it."  During  the  building  of  the  Duke  of 
Devonshire's  house  at  Chiswick,  the  exterior  of  which 
was  plastered  with  stucco,  the  surrounding  district  was 
impoverished  for  eggs  and  butter-milk  to  mix  with  the 


128  CEMENTS  AND  CONCRETES 


stucco.  Peter  le  Neve's  mention  of  rye  dough  stands 
not  alone,  as  Sir  Christopher  Wren's  '^Parentalia"  * 
(1750)  records  the  use  of  '^marble  meal"  as  the  old  and 
still  the  modern  way  of  stucco  work  in  Italy.  ''Marble 
meal"  simply  meant  marble  dust  ground  as  fine  as  meal. 
This  dust  was  used  fo^  fine  work.  Sugar  a,nd  the  gluten 
of  rice  are  used  in  Ceylon  and  India.  The  Chinese  use 
a  rich  unctuous  earth  in  combination  with  lime.  In  some 
parts  of  Prance  urine  was  used  with  plaster  in  the  six- 
teenth century.  Nearly  all  these  admixtures  are  to  re- 
tard the  setting,  to  allow  more  time  for  the  manipulation 
of  the  stuccos.  Some  are  to  accelerate  the  setting,  and 
some  are  to  increase  their  ultimate  hardness. 

Many  of  the  ancient  buildings  in  various  parts  of  the 
universe,  which  were  built  of  mud,  clay,  or  sun-dried 
bricks,  had  their  surfaces  decorated  with  hand-wrought 
stucco.  During  explorations  in  Peru,  South  America, 
Dr.  Le  Plongeon  found  some  interesting  specimens  of 
ancient  plaster  work  in  a  number  of  the  ruins  of  the 
early  Peruvian  houses  and  cities,  which  date  back  to  re- 
mote antiquity.  At  Chenni  Concha  he  found  the  frag- 
ments of  some  ancient  ornamental  stucco  on  the  adobe 
(or  clay-built)  walls,  covered  with  bas-relief  decorative 
designs,  while  the  material  is  after  many  centuries  still 
in  good  preservation.  The  design  and  the  execution  are 
of  considerable  merit,  and  it  seems  wonderful  that  a 
people  ordinarily  held  to  be  but  little  better  than  savages 
could  have  conceived  ornamentations  so  sesthetic,  and 
have  executed  them  with  such  high  technical  ability. 

Cav.  M.  Geggenheim,  who  has  had  much  stucco  work 
done  in  the  Palazzo  Papadopoli  and  elsewhere,  gives  the 
following  formula  for  the  stucco  duro  which  is  still  used 
in  Venice:  It  is  old  stone  lime,  slaked  for  three  years 
at  least,  mixed  with  Carrara  marble  dust,  ground  as  fine 


TERMS  AND  PROCESSES 


129 


as  flour,  into  the  consistency  of  paste.  This  of  course 
is  for  the  finishing  coat,  the  rough  modelling  being  ex- 
ecuted with  a  coarser  material. 

There  are  four  kinds  of  so-called  stuccos  which  are 
used  in  this  country.  They  are  known  as  common,  rough, 
bastard,  and  trowelled.  The  methods  of  working  these 
species  of  plastering  are  embodied  in  the  description  of 
three-coat  work — in  fact  the  only  difference  between 
these  stuccos  and  three-coat  work  lies  in  the  setting  coat, 
the  first-coating  and  floating  being  the  same  for  all. 
Some  of  the  above  terms  are  now  only  used  by  work- 
men, and  the  use  of  stuccos  is  to  a  great  extent  super- 
seded by  Portland  cement  for  exterior  work,  and  Parian 
and  other  white  cements  for  interior  work.  The  follow- 
ing is  a  summary  of  the  materials  and  methods  used  for 
the  various  stuccos. 

Common  Stucco. — Common  stucco  was  principally 
used  for  exterior  work.  It  is  composed  of  3  parts  of 
coarse  sharp  sand  to  1  of  hydraulic  or  grey  lime,  to  which 
a  small  portion  of  hair  is  added.  It  is  laid  in  a  similar 
way  to  ordinary  rendering  in  one  coat,  and  the  surface 
finished  with  a  hand  float. 

Bough  Stucco. — This  is  generally  used  for  plastering 
churches,  corridors,  and  entrance  halls  to  imitate  stone. 
The  work  is  floated  with  ordinary  coarse  stuff,  and  then 
set  with  stuff  composed  of  3  parts  of  washed  sharp  sand 
and  2  of  grey  lime  putty,  not  chalk.  This  is  laid  with 
a  trowel,  and  then  ruled  in  with  a  straight  edge  until 
the  surface  is  full  and  fair.  After  this  it  is  scoured 
with  an  ordinary  hand  float,  and  finished  with  a  ^^felt 
float,''  not  to  raise  the  grit,  but  to  keep  it  down.  The 
felt  float  is  an  ordinary  hand  float  with  an  unplaned 
sole,  on  which  a  felt  sole,  about  14  i^^h  thick,  is  fixed 
with  gauged  plaster.    This  tool  before  using  generally 


130 


CEMENTS  AND  CONCRETES 


requires  to  be  riiDbeci  on  a  str^aight  stone  to  obtain  a  uni- 
form face.  Great  care  must  be  exercised  when  laying 
and  finishing  the  surface,  so  that  no  joints  are  shown, 
or  else  they  w^ill  never  dry  out.  AVhen  wanted  to  repre- 
sent ashlar  masonry,  the  surface  is  set  out  with  lines  to 
the  size  of  the  required  stones,  and  then  the  lines  are 
indented  to  form  the  joints  with  a  jointer  or  the  ring 
end  of  a  key.  The  grain  of  the  stone  can  be  better  imi- 
tated by  patting  the  surface  with  the  hand  float  as  a 
finish.  The  staining  of  stucco  to  represent  the  color  of 
stone  is  done  by  diluting  sulphuric  acid  (oil  of  vitriol) 
with  water,  and  mixing  with  it  the  liquid  ochres  and 
other  colors  to  the  required  tints.  The  setting  stuff  may 
also  be  mixed  with  the  ochres  before  using.  A  small  por- 
tion of  the  colored  stuff  should  be  dried  to  ascertain  the 
tints  before  laying  the  whole  surface. 

Bastard  Stucco  is  somewhat  better  in  quality  than  or- 
dinary setting.  The  final  coat  is  composed  of  2^2  parts 
of  washed  sharp  sand  and  2  parts  of  chalk  lime  putty. 
It  is  laid  in  two  coats  with  a  skimming  float,  scoured  up 
once  and  then  trowelled  oft'  and  brushed. 

Trowelled  Stucco  is  generally  used  for  work  that  has 
to  be  subsequently  painted.  The  stuff'  for  the  finishing 
coat  is  composed  of  fram  2^  to  3  parts  of  washed  sharp 
sand  to  2  parts  of  chalk  lime  putty.  The  sand  is  not  so 
fine  as  that  used  for  ordinary  setting,  being  washed 
through  a  sieve  having  about  12  mesh  to  the  inch.  The 
stuff  is  laid  on^  and  then  traversed  with  a  floating  rule 
in  all  directions,  up  and  down,  across  and  diagonally. 
The  surface  is  then  scoured  up  without  water,  and  after 
a  rest  to  admit  of  shrinkage,  the  surface  is  scoured  up 
three  times  with  water ;  the  trowel  to  immediately  follow 
the  third  scouring  up.  This  trowelling  is  continued 
until  the  work  becomes  so  hard  that  no  impression  can 


TERMS  AND  PROCESSES 


131 


be  made  on  the  surface;  it  is  then  brushed  off  with  a 
soft  damp  brush  (not  wet),  first  horizontally,  then  diag- 
onally, and  finally  perpendicularly,  leaving  a  brilliant 
face.  When  dry,  the  gloss  goes  off,  and  leaves  a  fine 
surface  for  paint. 

Colored  Shtcco. — The  Italians  execute  lime  stuccos  in 
colors,  mixing  in  the  lime  various  oxides — i.  e.,  blacks 
are  obtained  by  using  forge  ashes  containing  particles  of 
iron;  pearl  greys  are  made  by  mixing  ashes  with  the 
marble;  greens  are  obtained  by  using  green  enamel,  with 
a  large  proportion  of  marble  powder,  worked  up  with 
lime-water;  browns  by  mixing  ashes  with  the  lime  and 
marble  in  proportions  varying  with  the  tints  desired; 
reds  by  using  litharge,  or  the  red  oxide  of  lead;  blues 
by  r^iixing  2  parts  of  marble  powder  and  1  of  lime,  and 
1/4  of  oxide,  or  carbonate  of  copper.  Stucco  may  also 
be  colored  with  the  same  materials  as  described  for 
colored  setting,  also  for  sgraffito  and  concrete. 

MetJiod  of  Wo7^king  Keen's^  Parian,  and  Martinis 
Cements. — When  describing  the  technique  or  practical 
manipulation  of  Parian  and  the  other  white  cements 
which  have  been  invented  in  the  nineteenth  century,  it 
is  only  natural  that  one  should  feel  animated  by  a  pecu- 
liar pleasure,  because  in  these  cements,  our  industry, 
aided  by  modern  science,  has,  as  far  as  is  known, 
equalled,  if  not  excelled,  an^^thing  of  the  kind  produced 
by  the  ancients,  tested  by  any  experiment,  whether  for 
strength,  solidity,  or  durability.  With  these  a  great  sav- 
ing in  time  can  be  effected,  as  work  can  be  begun  and 
finished  in  one  operation,  without  waiting  for  the  differ- 
ent coats  to  dry,  as  in  ordinary  lime  plastering.  For 
sanitary  purposes  they  are  unequalled.  This,  combined 
with  their  chemical  properties,  which  enables  them  to  be 
painted,  papered,  or  distempered  as  soon  as  finished, 


132  CEMENTS  AND  CONCRETES 


renders  them  the  most  valuable  of  all  plastering  materials 
in  this  go-ahead  age.  They  are  free-working,  sanitary, 
durable,  and  practically  fireproof.  They  are  the  very 
best  materials  for  plastering  walls,  dadoes,  or  in  similar 
exposed  positions.  For  skirtings  they  are  invaluable, 
as  they  offer  an  effectual  resistance  to  fire,  vermin,  and 
dust.  When  properly  manipulated,  they  can  be  worked 
to  a  porcelain-like  surface.  They  are  nearly  perfection, 
and  constitute  perfect  plasters  for  most  interior  work. 
Their  only  drawback  is  that  they  will  not  resist  the  ef- 
fects of  moisture.  It  is  therefore  imperative  that  damp 
walls  should  be  floated  with  Portland  cement,  where 
a  white  cement  finish  is  desirable.  By  the  aid  of  the 
hard  and  sanitary  white  cements  plastering  has  become 
a  tangible  reality,  instead  of  a  comparative  makeshift, 
which  it  has  hitherto  been.  The  object  aimed  at  in  the 
invention  of  white  cements  for  internal  use  is  to  pro- 
duce a  material  of  which  plaster  is  the  base,  which  shall 
set  sufficiently  slow  to  be  easily  manipulated,  become 
dense,  hard,  non-porous,  and  may  be  painted  as  soon  as 
finished.  Before  the  introduction  of  these  cements,  all 
making  good,  as  it  is  technically  called  (i.  e.,  patching 
holes  in  old  plaster  work),  used  to  be  done  with  neat 
plaster,  plaster  and  sand,  or  lime  gauged  with  plaster. 
Keen's  was  first  introduced,  then  Parian,  and  lastly 
Martin 's.  Parian  being  most  in  demand,  claims  priority 
in  description.  Parian  and  other  white  cements  are  uni- 
formly reliable  in  quality,  but  through  the  rapacity  of 
some  contractors  the  cements  are  often  adulterated  with 
plaster  to  lower  the  cost,  and  hasten  their  setting.  This 
adulteration  causes  the  cement  to  swell^  and  in  many  in- 
stances to  peel  or  fall  off.  Even  if  it  does  adhere,  it 
never  attains  its  due  hardness,  and  thus  is  no  better  than 
ordinary   plaster.    Unfortunately   adulteration  brings 


TERMS  AND  PROCESSES 


133 


discredit  on  the  cement  and  the  trade.  The  only  remedy 
is  proper  supervision  by  a  plasterer  who  possesses  a  thor- 
ough knowledge  of  plastic  materials  and  the  methods  of 
using  them.  If  plasterers  were  awarded  certificates  of 
competency,  adulteration  would  be  prevented,  and  good 
work  ensured.  Honest  employers  would  find  this  bene- 
ficial, for  scampers  can  only  thrive  where  there  is  a  lack 
of  knowledge  of  the  technique  peculiar  to  plastering, 
and  which  only  plasterers  of  experience  really  possess. 

In  using  Parian  cement  on  lath-work,  exceptional  care 
must  be  observed  that  all  the  lath  nails  be  galvanized, 
or  painted  over,  or  coated  with  shellac,  to  prevent  rust. 
For  this  same  reason  all  nails  used  for  plumbing  and 
levelling  purposes  must  be  extracted  after  the  screeds 
are  set.  For  first-coating  and  floating  ceilings  with  this 
material,  the  proportions  for  best  work  are  1  part  of 
cement  to  2  of  clean  sharp  sand,  adding  about  the  same 
quantity  of  hair  as  for  lime  plaster.  Walls  are  generally 
floated  with  Portland  cement  in  the  proportion  of  1  part 
of  cement  to  3  of  sand,  and  finished  with  neat  Parian. 
This  system  is  adopted  as  a  matter  of  economy,  as  Port- 
land cement  is  cheaper  than  Parian;  and  where  time  is 
no  particular  object,  makes  equally  as  good  work.  For 
walls  intended  to  be  painted  or  polished  immediately,  it 
is  necessary  to  mix  the  materials  in  the  same  proportion 
as  for  ceilings,  with  the  difference  that  more  sand  may 
be  used — say  2  parts  of  cement  to  5  of  sand.  The  rea- 
son for  this  is,  that  when  floated  with  Portland,  and 
finished  with  Parian  an  efflorescence  invariably  appears 
on  the  finished  surface,  and  until  it  has  time  to  dry  out, 
it  is  inimical  to  successful  painting  or  polishing.  Gaug- 
ing is  an  important  point;  it  must  be  carefully  and 
quickly  done  to  insure  success  and  obtain  the  full 
strength  of  the  cement.    For  first-coating  or  floating 


134  CEMENTS  AND  CONCRETES 


ceilings,  empty  a  sackful,  or  half  a  sack  according  to 
requirements,  in  a  clean  banker;  then  add  the  sand  in 
the  proportions  already  given,  and  thoroughly  mix  the 
cement  and  sand  while  yet  dry ;  then  form  a  ring,  and 
pour  in  the  water,  taking  care  not  to  pour  in  too  much, 
as  it  must  be  gauged,  and  used  as  stiff  as  practicable. 
There  will  be  no  difficulty  in  thus  using  it,  as  it  will  take 
some  hours  to  set,  according  to  the  season  of  the  year 
(quicker  in  summer  than  in  winter).  When  the  , water 
is  in,  add  the  hair  (which  must  previously  be  well  beaten 
and  soaked),  and  gauge  the  whole  mass  together.  Then 
begin  the  first  coating,  scratch  it  in  the  usual  manner, 
and  so  on,  until  the  whole  ceiling  is  first-coated.  It 
should  stand  for  twenty  hours  before  starting  to  float. 
Hair  is  generally  omitted  for  common  work,  or  where 
the  laths  are  close. 

Parian  cement  ceilings  should  be  dead  level,  and  have 
a  uniform  and  straight  surface;  therefore  the  screeds 
should  be  levelled,  made  narrow,  and  the  sides  cut  square, 
and  when  firm  the  whole  ceiling  should  be  ruled  in  with 
a  floating  rule, ,  sufficiently  long  to  reach  from  screed  to 
screed.  The  floating  stuff  is  gauged  moderately  stiff, 
and  laid  diagonally  across  the  line  of  laths,  so  as  not  to 
spring  the  lath-work,  or  disturb  the  key  of  the  first-coat- 
ing. After  the  ceiling  has  been  laid,  the  floating  rule  is 
applied,  a  man  holding  each  end  (and  one  at  the  center 
if  extra  long).  It  is  then  drawn  gently  and  steadily 
along,  filling  up  hollow  places,  until  the  whole  surface 
is  straight  and  true.  When  the  surface  is  firm,  it  is 
brushed  with  a  coarse  broom  to  form  a  key  for  the  finish- 
ing coat.  If  there  is  a  Parian  cement  cornice  to  be  run, 
the  usual  mode  for  plaster  and  putty  is  adopted  for  the 
running  rules.  The  screeds  should  be  made  sufficiently 
smooth  to  run  on,  without  forming  an  extra  thickness  or 


TERMS  AND  PROCESSES  135 


traversing  screed.  The  cornice  is  roughed  out  with  the 
same  kind  of  material  as  used  for  the  floating,  employ- 
ing a  muffled  running  mould  for  running  the  rough  stuff. 
It  may  not  be  practical  to  rough  out  all  the  cornice  at 
once,  as  this  stuff  does  not  set  quick,  therefore  it  may  be 
necessary  to  leave  it  for  a  time  until  the  stuff  stiffens. 
No  definite  directions  can  be  laid  down  in  this  matter,  as 
the  suction  is  greater  in  some  seasons  and  rooms  than  in 
others.  A  little  extra  hair,  also  extra  stiff  gauging,  is  of 
service  to  make  the  stuff  cling  together,  thus  allowing 
the  work  to  be  roughed  out  sooner.  The  running  moulds 
must  be  made  of  strong  zinc  or  copper  (no  iron  to  be 
used  on  any  account).  Where  the  work  is  in  cornices, 
skirtings,  achitraves,  &c.,  the  mould  should  be  muf- 
fled with  a  zinc  or  copper  plate.  If  there  is  only  a  small 
quantity  to  be  run,  a  plaster  muffle  may  suffice.  After 
the  cornice  is  roughed  out,  it  is  finished  with  neat  Parian, 
and  then  the  mitres  formed  in  the  usual  way. 

In  preparing  to  finish  a  large  space  (ceilings  or  walls) 
it  is  absolutely  necessary  that  no  more  should  be  laid 
than  can  be  finished  the  same  day,  therefore  as  many 
ihen  should  be  put  on  the  job  as  will  accomplish  that 
object,  as  no  sign  of  a  joint  should  be  shown  on  the  sur- 
face. In  the  case  of  large  or  high  walls,  the  scaffold 
should  be  so  arranged  that  the  men  can  work  the  whole 
wall  from  the  cornice  down  to  the  skirting  in  one  opera- 
tion. If  a  wooden  skirting  has  to  be  subsequently  fixed, 
one  end  of  the  rule  bears  on  the  fixing  grounds ;  but  if  a 
Parian  skirting  or  base  is  specified,  it  is  generally  run 
before  the  walls  are  finished,  and  allowed  to  get  thor- 
oughly hard,  so  as  to  bear  the  end  of  the  rule  used  for 
the  finishing  coat.  The  lower  end  of  the  rule  is  cut  to 
fit  the  upper  member  of  the  skirting.  Another  way  is 
to  nail  a  board  onto  the  end  of  the  rule,  so  that  it  bears 


136  CEMENTS  AND  CONCRETES 


well  on  the  plain  plinth  and  clears  the  members  of  the 
skirting.  The  cornice  screed  must  be  keyed  with  a  drag 
before  the  finishing  coat  is  laid.  For  large  cornices  it 
is  often  desirable  to  traverse  the  running  screeds.  In 
this  case  they  must  be  cut  down  to  the  floating,  leaving 
only  the  margin  formed  by  the  running  mould.  This 
margin  forms  a  bearing  for  the  top  end  of  the  rule.  In 
some  instances  a  special  margin  or  bearing  is  cut  at  the 
outer  members  of  running  moulds  for  cornices  and  skirt- 
ings, and  when  run  they  form  a  bearing  for  the  floating 
rules. 

When  ready  for  the  finishing  coat,  empty  as  much  as 
required  of  neat  Parian  cement  into  a  clean  banker,  and 
gauge  it  smooth  and  stiff;  then  soften  it  down  to  the 
desired  consistency,  always  bearing  in  mind  not  to  make 
it  too  soft,  as  sloppy  stuff  for  any  purpose  is  ever  to 
be  avoided.  The  gauging  should  be  so  arranged  that 
when  one  batch  is  in  use  another  one  is  ready,  which 
prevents  delay  in  laying  the  whole  space,  thereby  ensur- 
ing similarity  of  texture  and  results.  The  thickness  of 
the  finishing  coat  should  not  exceed  %  inch.  "When 
there  are  about  a  dozen  yards  laid,  two  men  must  follow 
on  and  rule  the  surface  fair  from  screed  to  screed  on 
ceilings,  and  top  and  bottom  on  walls.  The  greatest  pos- 
sible care  must  be  observed  that  the  whole  surface  is 
ruled  in  fair  and  uniform,  otherwise  the  surface  will  be 
imperfect. 

White  cements,  owing  to  the  suction  of  the  walls  or 
ceilings,  have  a  tendency  to  shrink  more  or  less,  accord- 
ing to  the  stiffness  of  the  gauge  and  the  section,  there- 
fore they  must  be  ruled  in  twice.  When  the  coat  already 
laid  is  firm,  then  some  more  cement,  gauged  softer  than 
the  first,  should  be  laid  thinly  all  over,  and  ruled  as  care- 
fully as  before.    Having  done  this  the  whole  surface  is 


TERMS  AND  PROCESSES  137 


nearly  ready  for  scouring;.  It  is  allowed  to  stand  for  an 
hour  or  two,  or  until  quite  firm.  If  scouring  is  at- 
tempted before,  it  will  work  into  hollows,  and  a  bad  job 
will  be  the  result.  If  the  finger  cannot  make  an  im- 
pression upon  it  easily,  it  is  sufficiently  firm,  and  then 
all  hands  begin  to  scour  the  work,  using  very  little  water, 
and  working  the  hand  float  with  a  circular  motion.  The 
hand  float  must  not  be  worked  long  on  one  spot,  but  kept 
moving  over  all  the  surface  within  reach,  and  working 
back  again  until  the  whole  surface  has  an  even  grain  or 
texture.  The  whole  work  must  be  scoured  twice  to  bring 
it  up  to  a  fine  solid  surface.  When  there  is  about  half 
of  the  wall  scoured,  two  or  more  plasterers  can  continue 
the  scouring,  and  the  remainder  of  the  men  go  back  and 
start  the  trowelling.  This  must  be  done  with  good  long 
strokes,  using  very  little  water,  and  taking  care  not  to 
dent  the  surface  with  the  trowel.  After  the  men  have 
finished  the  scouring,  they  come  back  and  start  at  the 
beginning  with  the  second  ''trowelling  off  or  final 
trowelling.  This  is  done  both  vertically  and  horizon- 
tally, and  when  the  work  begins  to  harden,  the  trowel  is 
laid  on  the  near  edge  and  worked  with  a  cutting  motion 
downwards.  This  is  repeated  all  over  the  work  until 
every  particle  of  glut  or  ' '  fat ' '  is  cleared  off  the  surface. 
If  the  work  has  to  be  polished,  the  cutting  action  with 
the  trowel  must  be  followed  with  a  9-inch  joint  rule  and 
a  damp  brush,  but  the  work  must  be  hard  before  this 
last  can  be  attempted.  Work  carried  out  on  the  above 
plan  v\^ill  reflect  credit  on  the  material  and  the  workers. 
The  same  methods  apply  equally  to  Keen 's  and  Martin 's. 
Martin's  is  preferred  by  some  plasterers  for  running 
cornices  because  it  sets  quicker  than  Keen's.  For  plain 
surfaces,  such  as  w^alls  and  ceilings,  it  sets  too  quick? 
and  has  to  be  ''killed"  (that  is  working  the  stuff  again 


138  CEMENTS  AND  CONCRETES 


and  again  with  water  until  the  initial  set  is  stopped  or 
''dead")  before  it  can  be  conveniently  used.  Although 
it  finally  sets  fairly  hard,  it  never  attains  the  same  de- 
gree of  hardness  as  Keen's  or  Parian. 

Several  other  white  cements  and  plasters  have  been 
introduced  during  the  last  two  decades.  They  will  be 
noticed  later  on. 

White  Cement  Efflorescence. — For  work  that  has  to 
be  painted,  care  must  be  exercised  in  the  selection  and  \ 
manipulation  of  the  materials  used  for  the  plaster  work, 
so  as  to  avoid  as  far  as  possible  subsequent  efflorescence. 
In  the  manufacture  of  Keen's,  Parian,  and  Martin's 
cements,  Keen's  original  process  is  doubtless  the  best. 
It  requires,  however,  great  care  in  carrying  out,  the 
chemicals  used  and  temperature  employed  requiring  to 
be  suited  to  the  peculiarities  of  the  gypsum.  The  de- 
sired result  is  extreme  hardness,  combined  with  non-ef- 
florescence. Keen's  cement  is  practically  non-efflores- 
cent, as  if  applied  on  a  dry  wall  containing  no  soluble 
salt,  in  itself  there  would  be  no  efflorescence  that  would 
spoil  paint.  Perhaps  one  should  not  say  that  Keen's 
cement,  or  at  least  all  brands  of  it,  are  absolutely  non- 
efflorescent,  as  there  is  generally  a  powdery  coating  comes 
on  the  surface,  just  enough  to  whiten  a  colored  hand- 
kerchief, something  like  the  coat  of  puff  powder  used 
on  some  female  faces.  On  no  account  should  Keen's 
cement  be  used"  on  walls  as  a  preventive  of  damp,  as 
it  is  useless  for  this  purpose.  If  used  on  a  damp  wall, 
or  in  places  exposed  to  atmospheric  influences,  it  will 
effloresce  more  or  less,  as  its  base  is  gypsum,  which  al- 
ways remains  soluble.  In  damp  situations  the  walls 
should  be  rendered  or  floated  in  Portland  cement  before 
the  finishing  coat  of  Keen's  cement  is  laid.  The  same 
remarks  apply  to  Parian  and  Martin's  cements.  The 


TERMS  AND  PROCESSES 


139 


Keen's  cement  manufactured  by  Hunkin's  and  Willis, 
St.  Louis,  Mo.,  is  practically  non-efflorescent. 

Cornice  Brackets. — Brackets  or  cores  are  used  to  de- 
crease the  amount  of  materials  and  weight,  and  also  to 
form  a  foundation  and  support  for  cornice  or  other 
mouldings.  For  large  exterior  work  they  are  generally 
formed  with  stone,  and  for  small  work  bricks,  tiles,  or 
slates  are  used,  which  are  built  into  the  walls  as  the 
work  proceeds,  and  roughly  fashioned  to  an  approxima- 
tion to  the  profile  of  the  intended  cornice  or  other  mould- 
ing. For  interior  work  the  brackets  are  sometimes  con- 
structed with  metal  lathing,  also  with  spikes  and  tar 
bands,  termed  ' '  spike  and  rope  brackets, ' '  but  the  oldest 
and  most  general  way  for  cornice  mouldings  are  "lath 
brackets.''  The  "brackets"  on  which  the  laths  are  sub- 
sequently nailed  are  cut  out  of  boards  from  %  inch  to 
11/2  inches  thick,  according  to  the  size  and  form  of  the 
cornice.  The  section  of  the  brackets  should  be  about  1 
inch  less  than  the  profile  of  the  proposed  cornice  to  allow 
for  a  thickness  of  lath  and  plaster.  The  thickness  of  the 
plaster  should  not  exceed  1  inch,  or  be  less  than  I/2  inch. 
If  too  thick  it  is  a  waste  of  materials,  and  the  undue 
weight  is  apt  to  pull  or  spring  the  laths  from  the  brack- 
ets, and  if  too  thin  the  stuff  is  apt  to  crack.  The  profile 
of  the  bracket  need  not  follow  closely  that  of  the  cor- 
nice, but  a  general  or  approximate  outline  of  the  most 
salient  members  followed.  Any  thin  projecting  mem- 
bers may  be  subsequently  strengthened  by  means  of 
projecting  nails  and  tar-strings  similar  to  a  spike  and 
rope  bracket ;  also  by  using  extra  hair  and  plaster  in  the 
roughing  out  stuff.  Brackets  for  enriched  cornices  re- 
quire special  notice.  Unless  a  due  allowance  is  made  for 
sinkings  for  the  thickness  of  the  cast  enrichments  and 
a  correct  form  of  bed,  there  will  be  unnecessary  trouble 


140  CEMENTS  AND  CONCRETES 


in  cutting  and  hacking  the  lath  work  and  brackets  when 
the  running  of  the  cornice  is  commenced.  There  is  a 
marked  difference  between  the  section  of  a  running 
mould  for  an  enriched  cornice  and  that  of  a  plain  cor- 
nice, even  if  the  profile  of  both  are  the  same.  To  avoid 
mistakes  of  this  nature  the  plasterer  should  supply  the 
carpenter  with  a  section  of  the  brackets,  taken  after  the 
bed  of  the  enrichments  are  set  out  on  the  tracing  of  the 
proposed  cornice. 

Skeleton  brackets  is  a  term  applied  to  a  method  some- 
times used  for  coring  out  angles,  to  save  materials  where 
there  are  no  brackets,  and  for  small  mouldings.  This  is 
effected  by  placing  the  mould  in  position  and  then  fitting 
a  piece  of  lath  in  a  vertical  position,  and  allowing  a  space 
of  about  %  inch  from  the  face  of  the  lath  to  the  nearest 
part  or  most  prominent  member  of  the  mould.  A  mark 
is  then  made  on  the  ceiling  and  wall  at  the  top  and  bot- 
tom of  the  lath.  Similar  marks  are  made  at  the  other 
end  of  the  wall  and  ceiling,  and  then  a  line  is  struck  on 
the  marks,  from  end  to  end  of  the  ceiling  and  wall,  by 
means  of  a  chalk  line.  The  stuff  which  forms  the  parts 
of  the  screeds  inside  the  lines  is  cut  away,  dusted,  wetted, 
and  then  a  narrow  strip  of  gauged  coarse  stuff  is  laid 
along  the  lines  where  the  ceiling  and  wall  screeds  are 
cut,  and  the  laths  which  have  been  previously  cut  to  the 
length  of  the  first  or  trial  one  are  fixed  vertically  into 
the  gauged  stuff,  keeping  them  apart  as  in  ordinary  lath- 
ing. They  are  further  secured  by  laying  strips  of 
gauged  stuff  on  the  outward  surfaces  at  the  top  and  bot- 
tom ends.  After  the  stuff  is  set,  the  cornice  is  run  in 
the  usual  way. 

Cornices. — Cornices,  either  plain  or  enriched,  are 
formed  with  a  running  mould  cut  to  the  profile  of  the 
intended  cornice.    The  formation  of  cornices  consists  of 


TERMS  AND  PROCESSES 


141 


constructing  the  mould,  making  the  running  screeds, 
fixing  the  running  rules,  running  the  cornice  and  mitring 
the  angles,  with  the  addition  of  fixing  the  cast  ornament 
for  enriched  cornices.  Cornices  were  formerly  run  in 
short  lengths  and  in  sections.  Two,  three,  and  even  four 
moulds  were  employed  for  cornices  that  are  now  done 
with  one.  For  large  cornices,  where  the  mould  is  diffi- 
cult or  sluggish  to  run,  or  apt  to  jump,  the  bearings 
should  be  greased  or  brushed  with  soap  or  dusted  with 
powdered  black  lead  or  French  chalk.  Running  moulds 
are  run  in  some  places  with  the  left  hand,  from  left  to 
right,  and  the  mould  plates  are  also  fixed  to  the  left  hand 
side,  having  the  bevelled  part  of  the  stock  to  the  right 
or  running  side.  In  America  the  plates  are  fixed  oh  the 
running  or  right  side,  and  the  mould  is  run  with  the 
right  hand  from  right  to  left.  The  way  of  running  from 
left  to  right  with  the  left  hand  allows  more  freedom, 
especially  in  small  mouldings,  for  the  right  or  trowel 
hand  to  assist  in  feeding  the  cornice  with  the  stuff  that 
gathers  on  the  mould.  It  also  gives  more  freedom  to 
his  partner  who  is  laying  on  the  stuff,  as  with  the  hawk 
in  his  left  hand  and  his  trowel  in  his  right  he  is  able  to 
work  in  a  natural  position,  namely,  from  left  to  right,  as 
in  laying  coarse  or  setting  stuff  on  w^alls,  whereas,  when 
the  mould  is  run  with  the  right  hand,  and  from  right  to 
left,  the  worker  has  not  so  much  power  or  freedom  in 
assisting  to  feed  the  mould  with  his  left  hand.  His  part- 
ner, who  is  laying  the  gauged  stuff,  is  working  back- 
handed, and  if  using  a  laying  trowel,  can  only  work  from 
its  heel  instead  of  from  the  point  as  is  usual;  and  if 
using  the  large  gauging  trowel  for  laying  on  every 
trowelful  used  must  be  put  on  with  a  backhanded  turn. 
It  may  be  a  matter  of  opinion  as  to  which  method  is 
better,  and  depends  a  good  deal  upon  which  way  the  man 


142  CEMENTS  AND  CONCRETES 


has  been  taught,  but  the  manner  of  running  the  mould 
and  laying  on  of  stuff  from  left  to  right,  the  same  as 
in  writing,  is  the  most  natural.  Running  screeds  are 
used  as  bearings  for  running  moulds.  They  are  com- 
posed of  gauged  stuff,  and  made  straight  with  floating 
rules.  Screeds  for  cornices  are  formed  with  -raw  or  with 
gauged  coarse  stuff.  They  are  next  traversed.  The 
line  of  the  screed  is  got  by  placing  the  running  mould 
in  its  true  position  or  at  one  end  of  the  wall,  and  mak- 
ing a  mark  on  the  floating  screeds  at  the  outside  of  the 
nib  and  the  bottom  of  the  slipper.  The  same  operation 
is  repeated  at  the  other  end  of  the  wall,  and  a  continuous 
line  from  one  mark  to  the  other  made  on  the  ceiling  wall 
by  means  of  a  chalk  line.  A  narrow  strip  of  gauged 
putty  and  plaster  is  now  laid  on  the  lines  by  one  man, 
while  his  partner  follows  on  with  a  traversing  rule,  work- 
ing the  rule  with  a  slanting  motion,  and  moving  back- 
wards and  forwards  until  the  screed  is  just  and  true. 
Where  the  walls  are  very  long,  running  screeds  are  done 
by  two  men  working  a  long  straight  edge  or  floating 
rule.  The  screed  is  afterwards  further  fined  by  draw- 
ing a  cross-grained  hand  float  three  or  four  times  over 
it  in  a  longitudinal  direction.  Where  the  coarse  stuff 
screeds  are  not  gauged,  the  running  screeds  are  made  in 
a  similar  manner,  but  the  putty  is  mixed  with  an  equal 
proportion  of  setting  stuff  before  gauging.  The  addi- 
tion of  sand  gives  more  resisting  power  to  the  wear  of 
the  nib  and  slipper  of  the  running  mould.  The  run- 
ning screeds  are  made  on  the  long  sides  of  the  room, 
and  when  set  they  give  a  bearing  for  the  end  screed  in 
its  true  position  at  one  end  of  the  wall. 

Fixing  the  running  rules  is  the  next  operation.  This 
is  done  by  placing  the  running  mould  in  its  true  position 
at  one  end  of  the  wall,  taking  care  that  the  mould  is 


142  ( 


has  been  ta 
and  laying 
in  writing, 
used  as  hei 
posed  of  gi 
rules.  Scr( 
gauged  coa 
line  of  the 
in  its  true 
ing  a  mark 
nib  and  thi 
is  repeated 
line  from  o 
by  means  c 
putty  and  } 
while  his  pa. 
ing  the  ruh 
w^ards  and 
"Where  the  i 
by  two  mei 
rule.    The  i 
ing  a  cross- 
it  in  a  lonfj 
screeds  are  p 
a  similar  ml 
proportion  t 
tion  of  san| 
the  nib  anc 
ning  screed' 
and  when  s 
its  true  pos*  -^- 

Fixing  th 
is  done  by  i 
at  one  end 


TERMS  AND  PROCESSES  143 


square/'  that  is,  that  the  perpendicular  parts  of  mem- 
bers are  plumb  with  the  wall.    This  may  be  tested  with 
a  plumb  bob  hanging  over  the  side  of  the  mould,  and  by 
seeing  that  the  line  of  the  plumb  bob  hangs  properly  over 
a  marked  line  which  has  been  previously  made  by  squar- 
ing off  from  a  square  member  or  by  extending  a  parallel 
line  from  an  upright  member  of  the  mould.    When  the 
mould  is  plumb  and  square,  a  mark  is  made  on  the  ceil- 
j  ing  screed  at  the  outside  part  of  the  nib,  and  another 
made  on  the  wall  screed  at  the  bottom  of  the  slipper. 
The  same  operation  is  repeated  at  the  other  end  of  the 
wall,  and  the  line  extended  from  mark  to  mark  by  using 
a  chalk  line.    The  line  in  this  case  should  be  blackened 
by  means  of  charcoal  or  burnt  stick,  as  it  shows  better 
than  a  white  line  on  the  light-colored  screeds.    As  the 
chalk  line  may  sway  when  striking  the  wall  line,  this 
line  should  not  be  trusted  for  fixing  the  running  rules 
to.    This  may  be  proved  by  placing  the  mould  every  3 
or  4  feet  apart  in  the  length  of  the  wall,  taking  care  to 
keep  the  outer  edge  of  the  nib  at  the  ceiling  line;  then 
marking  with  a  gauging  trow^el  at  the  bottom  of  the  slip- 
per.   Nails  are  now  driven  into  each  of  these  marks  and 
left  projecting  as  a  guide  for  fixing  the  running  rules. 
The  running  rules  should  not  be  less  than  21/2  inches 
wide  or  more  than  31/^  inches  wide  and  i/^  inch  thick, 
being  made  out  of  good  redwood  or  pine  planed  on  both 
sides  and  edges.    The  rules  are  now  fixed  into  the  wall 
screed  either  by  nailing  them  to  the  studs  or  into  the 
joints  of  the  walls.    They  are  also  fixed  by  wetting  one 
face  of  the  rule  and  laying  dabs  of  gauged  putty  and 
plaster  about  two  feet  6  inches  apart.    The  rules  are 
now  pressed  on  the  wall  while  the  stuff  is  soft,  taking 
care  not  to  force  the  guide  nails  out  of  position.  The 
rules  are  further  secured  by  laying  patches  of  gauged 


144  CEMENTS  AND  CONCRETES 


stuff  underneath  the  rule  partly  on  the  wall  and  rule 
where  the  dabs  are.  "When  the  rules  are  fixed  by  nail- 
ing, it  is  apt  to  crack  the  first-coat  of  floating,  and  the 
joints  of  the  wall  are  not  always  easily  found.  The 
coarse  stuff  for  the  first-coat  of  cornice  brackets  should 
be  extra  haired  and  carefully  scratched  to  give  a  strong 
foundation  for  the  following  coats  of  gauged  stuff,  which 
in  many  instances  is  extra  thick  at  bold  or  projecting 
parts  of  the  mouldings. 

For  large  moulding  and  wire  lathing  it  is  best  to  leave 
the  brackets  uncoated  when  first  coating  the  general 
work  until  the  cornice  running  is  commenced,  and  then 
to  rough  out  the  whole  cornice  from  the  lath  work  with 
gauged  coarse  stuff.  This  gives  uniform  suction  and 
strength.  If  the  brackets  are  lathed  with  wood,  they 
should  be  first-coated  with  gauged  coarse  stuff  and 
scratched  before  the  screeds  are  formed,  so  as  to  allow 
time  for  the  lath  work  to  settle  before  the  mouldings 
are  roughed  out.  Weak  laths  frequently  twist  by  moist- 
ure from  the  first-coating,  and  gradually  settle  or  re- 
sume their  original  form  during  the  drying  of  the  first- 
coating.  Leaving  the  lathed  brackets  uncoated  also 
forms  a  vent  for  the  moisture  from  the  wall  and  ceiling 
first-coating,  thus  allowing  it  to  dry  sooner.  The  coarse 
stuff  for  roughing  out  the  cornice  should  be  gauged  uni- 
formly in  strength  and  consistency,  as  unequal  gauging 
tends  to  cause  unequal  swelling  in  the  material,  conse- 
quently the  mould  is  more  difficult  to  run  true.  The 
coarse  stuff  should  be  laid  regular  in  thickness,  taking 
care  to  gradually  build  up  and  form  all  thick  parts  and 
projecting  members  with  the  trowel  to  prevent  the  stuff 
from  dropping  and  the  mould  from  dragging  it  off,  as 
generally  happens  if  the  stuff  is  laid  in  thick  and  irregu- 
lar coats.    When  roughing  out  large  mouldings  with 


TERMS  AND  PROCESSES  145 


coarse  stuff,  the  members  of  the  mitres  should  also  be 
filled  in  and  ruled  fair  before  the  running  with  gauged 
putty  is  commenced,  because  when  mitring,  it  will  be 
more  easily  and  quickly  done,  materials  will  be  saved, 
and  when  finished,  the  whole  will  be  more  uniform  in 
color. 

When  all  the  mouldings  are  roughed  out,  the  plaster 
muffle  or  muffle  plate,  as  the  case  may  be,  is  taken  off, 
and  the  running  with  fine  gauged  putty  commenced. 
The  gauge  board  and  all  tools  should  now  be  cleaned  to 
free  them  from  grit.  A  ring  of  putty  is  formed  on  the 
gauge  board,  leaving  the  bottom  of  the  board  clear; 
water  is  put  in  the  ring  and  the  plaster  quickly  and 
evenly  sprinkled  over  the  water,  taking  care  not  to  sprin- 
kle it  on  the  putty  ring.  The  plaster  and  water  are 
mixed  together  by  stirring  with  the  point  of  a  trowel. 
The  putty  is  then  quickly  mixed  with  the  gauged  plaster 
by  using  the  trowel  and  turning  it  over  with  the  hawk. 
It  is  put  on  with  a  large  gauging  trowel,  or  if  the  mem- 
bers are  large,  with  the  laying  trowel,  following  the  form 
of  the  mouldings.  The  mould  is  then  run  along  by  one 
man,  who  also  feeds  the  moulding  with  any  stuff  that 
may  gather  on  the  side  of  the  running  mould.  This 
operation  is  continued  until  all  the  members  of  the 
mouldings  are  filled  out.  A  thin  gauge  of  fine  putty, 
having  less  plaster  than  the  previous  gauges,  is  lightly 
drawn  over  with  a  trowel,  or  brushed  over  the  flat  mom- 
bers,  and  thrown  with  a  brush  for  small  or  dry  mem- 
bers. This  mould  is  then  quickly  and  steadily  run  along 
the  cornice  from  beginning  to  end  and  finished.  If  the 
moulding  is  extra  large  in  girth,  or  a  long  length  of 
moulding  has  to  be  run,  extra  men  are  required  to  lay 
the  stuff,  while  two  may  be  necessary  to  run  the  mould. 


146  CEMENTS  AND  CONCEETES 


When  running  small  mouldings,  say  of  10  or  12  inches 
in  girth,  one  man  can  run  and  feed  the  mould  while  his 
partner  is  laying  on.  When  all  the  mouldings  are  run 
around,  the  running  rules  are  taken  down,  the  screeds 
cleaned  and  scraped,  and  any  holes  or  defects  caused 
by  nails  or  patches  used  for  the  rules  made  good  by  fill- 
ing up  with  gauged  putty.  If  soap,  black  lead,  or  any 
other  materials  already  mentioned  are  used  to  aid  and 
ease  the  running  of  the  mould,  they  should  be  scraped 
ofE  with  a  drag  as  soon  as  the  cornice  is  run  off,  other- 
wise they  will  prevent  the  finishing  coats  for  wall  and 
ceiling  from  adhering  to  those  parts. 

To  Set  Out  and  Construct  Corinthian  Entablature. — 
To  enable  the  plasterer  to  set  out  a  full  size  or  working 
drawing  from  the  architect's  design,  also  to  comprehend 
the  cornice  and  the  architrave,  which  are  sometimes  used 
alone  or  as  separate  mouldings,  their  proportions  with 
that  of  the  entire  entablature  are  given.  The  entabla- 
ture and  the  details  of  the  enrichments  of  the  coffers 
and  modillions  are  shown  on  plate. 

The  whole  height  of  the  entablature  is  divided  into 
ten  parts,  giving  three  to  the  architrave,  and  three  to 
the  frieze,  and  four  to  the  cornice,  as  shown  by  the  first 
upright  scale  at  Fig.  1.  This  figure  shows  the  combined 
section  and  elevation  of  the  entablature.  The  height 
of  the  architrave  is  subdivided  into  five  parts  to  form 
its  members,  as  shown  by  the  second  upright  scale. 
Projection  is  taken  from  the  lower  fascia,  and  is  equal 
to  one-fourth  part  of  its  height.  As  the  cornice  of  the 
Corinthian  order  is  frequently  used  alone  as  a  separate 
moulding,  an  enlarged  view  with  figured  details  is  given, 
see  illustration  Fig.  4.  It  is  necessary  that  the  details 
of  the  cornice  should  be  mastered  before  proceeding  with 
the  entablature.    See  Plate  1, 


TERMS  AND  PROCESSES  147 


With  regards  to  the  enrichments  of  the  entablature, 
as  shown  in  Fig.  1,  the  whole  must  be  set  out  and  so  dis- 
posed and  arranged  that  the  centre  of  each  will  be  in  line 
with  each  other,  or,  in  other  words,  that  they  are  regu- 
larly disposed  perpendicularly  above  each  other,  as 
shown  from  A  to  B  (Fig.  1)  where  it  will  be  seen  that 
the  centres  of  the  modillion,  dentil,  egg,  and  other  bed- 
mould  enrichments  are  all  in  one  perpendicular  line. 
Enrichments  set  out  in  this  v/ay  are  said,  in  plasterers' 
parlance,  to  ^ '  principle. ' '  Nothing  is  more  careless,  con- 
fused, and  unseemly  than  to  distribute  them  without 
any  order  or  principle,  as  they  are  in  many  buildings. 
The  centre' of  an  egg  answers  in  some  places  of  the  cor- 
nice to-  the  edge  of  a  dentil,  in  some  to  the  centre,  and 
in  others  to  the  space  between,  all  the  rest  of  the  enrich- 
ments being  distributed  in  the  same  slovenly  artless 
manner.  The  larger  parts  must  regulate  the  smaller. 
All  the  enrichments  in  entablatures  are  governed  by  the 
modillions,  or  mutales,  and  distribution  of  these  must 
depend  on  the  interval  of  the  columns,  and  to  be  so  dis- 
posed that  one  of  them  may  come  directly  over  the  centre 
of  the  column,  as  shown  in  the  present  example  at  0 
(Fig.  2),  the  axis  of  each  column. 

The  enrichments  must  partake  of  the  character  of  the 
order  they  enrich.  "When  the  frieze  is  enriched,  and  the 
enrichment  may  be  characteristic  of  the  order,  or  it  may 
serve  to  indicate  the  use  of  the  building,  the  rank,  quali- 
ties, profession,  and  achievements  of  the  owner.  Hav- 
ing set  out  the  profile  and  the  enrichments,  making  the 
running  mould  and  the  running  mouldings  now  claims 
attention.  For  large  work  the  cornice  and  the  archi- 
trave are  run  separately,  the  cornice  being  run  from  the 
slipper  screed  made  on  the  frieze  and  a  nib  screed,  and 
the  architrave  from  a  slipper  screed  made  on  the  wall 


148  CEMENTS  AND  CONCRETES 


and  a  nib  screed  made  on  the  frieze.  Sections  of  the 
cornice  and  architrave  running  moulds  are  shown  at 
Fig.  4. 

It  may  be  here  remarked  that  the  nib  and  slipper 
bearings  of  the  cornice  and  architrave  running  moulds 
are  made  for  work  on  ceilings  and  walls;  but  if  the 
entablature  projects  or  is  independent,  and  supported  by 
columns,  the  nib  of  the  cornice  mould  must  be  cut  so 
as  to  bear  and  run  on  a  nib  running  rule  fixed  on  the 
weathering  of  the  cornice,  and  the  slipper  of  the  archi- 
trave running  mould  cut  so  as  to  bear  and  run  on  a 
running  rule  fixed  on  the  soffit  of  the  architrave.  The 
frieze,  if  plain,  is  set  by  hand;  and  if  enriched,  a  bed 
for  the  enrichment  must  be  made  by  running  a  small 
part  of  the  bed  at  the  top  and  bottom  of  the  frieze  when 
running  the  cornice  and  architrave  mouldings.  In  this 
case  the  screed  on  the  frieze  must  be  set  back  to  allow 
for  the  plate  or  ground  of  the  ornament,  and  the  nibs 
and  slippers  of  the  running  moulds  extended  at  these 
parts.  In  setting  out  the  mould  plates  an  allowance 
must  be  made  for  the  bed  of  the  various  enrichments,  as 
previously  described. 

The  profiles  of  the  three  largest  enrichments  are  indi- 
cated by  the  dotted  lines.  The  angles  of  the  beds  of 
these  enrichments  are  splayed,  as  shown,  to  save  fine 
plaster  used  for  the  cast  work.  This  also  strengthens 
the  top  member  of  the  architrave  while  it  is  being  run. 
It  will  be  seen  that  an  in-dentil  is  used  in  this  cornice, 
as  shown  by  the  dotted  line  at  1  on  the  elevation.  This 
is  the  space  between  the  face  or  main  dentils.  The  in- 
dentil  is  run  with  the  mouldings,  and  the  dentils  are  cast 
and  planted.  The  in-dentil  and  the  dentil  may  also  be 
cast  together  in  short  lengths,  and  then  planted.  In 
this  case  the  running  mould  must  be  cut  to  form  a  bed 


TERMS  AND  PROCESSES 


149 


for  the  combined  dentils,  as  indicated  by  the  dotted  line 
on  the  outside  of  the  section  of  the  running  mould.  The 
dotted  line  on  the  section  of  the  running  mould  shows 
the  section  of  the  main  dentil.  In  some  examples  the 
external  angles  of  the  bed  of  the  dentils  are  filled  in  with 
an  ornament  fashioned  like  a  cone  or  pineapple,  instead 
of  using  an  angle  dentil.  An  enlarged  view  of  this  class 
of  ornament  fixed  in  position  is  shown  at  Fig.  11.  The 
bed  of  the  small  enrichments  is  made  square  as  shown. 

When  setting  out  the  mould  plate,  the  profile  of  the 
soffit  of  the  corona  must  be  taken  through  the  centre  of 
the  sunk  panel,  as  shov/n  by  the  shaded  part  at  Fig.  3, 
thus  forming  the  raised  part  of  the  mould  as  shown  at 
Fig.  4. 

The  most  intricate  part  in  the  construction  of  a  Cor- 
inthian cornice  consists  in  the  formation  of  the  coffers, 
as  shown  at  Fig.  2.  This  is  a  plan  of  the  cornice  at  an 
external  angle.  F  is  a  coffer,  and  M  is  a  modillion  or 
''block,"  as  it  is  commonly  called.  The  coffer  consists 
of  a  sunk  panel,  with  an  enrichment  on  the  four  sides, 
and  a  rose  or  patera  in  the  centre  as  shown.  A  section 
of  the  coffer  is  showni  at  Fig.  3.  The  coffers  are  formed 
by  fixing  a  ''style,"  as  from  S  to  S  (including  the  side 
enrichments),  on  the  sunk  panel,  so  as  to  connect  the 
two  run  plain  sides  of  the  soffit  and  form  two  sides  of 
the  coffer.  The  lines  in  the  front  and  back  of  S  and 
S  indicate  the  joints  of  the  style  before  they  are  stopped. 
It  will  be  understood  that  the  style  is  fixed  before  the 
block  is  fixed.  A  plan  of  the  complete  style  is  shown  at 
Fig.  5.  When  making  the  model  of  the  style,  the  side 
enrichments  must  be  set  out  mitred  and  fixed  on  the 
plain  part  of  the  style,  and  a  perforation  made  in  the 
centre  to  act  as  a  key  for  the  fixing  stuff  used  when 
fixing  the  block.    A  mark  must  also  be  made  in  the  cen- 


150  CEMENTS  AND  CONCRETES 


tre  of  the  front  of  the  style  to  act  as  a  guide  when  fixing 
the  styles.  The  model  of  the  style  is  moulded  in  wax, 
taking  care  to  splay  the  back  and  front  edges  and  the 
centre  perforation,  also  the  mitres  of  the  enrichments, 
to  allow  the  mould  to  draw  in  one  piece.  These  parts 
are  trimmed  square  after  the  styles  are  cast.  Having 
fixed  two  styles,  the  front  and  back  parts  of  the  coffer 
enrichments,  as  shown  at  Figs.  6  and  7,  are  fixed;  then 
the  patera  (Fig.  8)  is  fixed;  and  then  the  joints  of  the 
styles  are  stopped,  which  completes  the  coffer.  This 
done,  the  block  (Fig.  9)  is  fixed,  and  then  the  small  en- 
richment (Fig.  10)  is  fixed,  thus  completing  a  part  of 
the  soffit  of  the  corona.  The  other  parts  are  of  course 
made  and  fixed  in  a  similar  way,  but  the  positions  of 
the  coffers  and  blocks  must  be  set  out  on  the  whole 
length  of  the  cornice  before  the  fixing  is  commenced. 

Setting  out  coffers  and  blocks  is  a  simple  matter,  yet 
it  requires  care  to  ensure  accuracy.  First  fix  a  coffer 
and  a  block  in  each  mitre,  as  shown  at  the  external 
mitre  (Fig.  2)  ;  then  from  the  centres  of  these  blocks  set 
out  the  whole  length  of  the  cornice.  This  is  best  done  by 
measuring  the  full  length  of  the  cornice  from  the  mitre 
blocks,  and  dividing  the  total  by  the  combined  width  of 
one  modillion  and  a  coffer,  and  if  there  is  no  remainder, 
the  combined  width  is  marked  on  the  soffit ;  but  if  there 
are  a  few  inches  over,  they  are  divided  among  the  given 
number  of  blocks.  The  marks  are  proved  by  going  over 
them  with  a  compass  or  a  wood  gauge.  When  the  exact 
positions  of  the  centres  of  each  coffer  with  the  block  is 
ascertained,  the  marks  are  extended  across  the  corona 
and  down  the  plain  member  on  which  the  back  end  of 
the  block  rests  on  by  the  aid  of  a  square.  These  ex- 
tended marks  or  lines  give  the  centres  for  fixing  the 
styles  of  the  coffei's  and  the  blocks.    Fixing  the  coffers 


TERMS  AND  PROCESSES 


151 


and  the  blocks  is  the  next  part  of  the  process.  This 
being  done,  as  already  described,  taking  care  to  use  the 
centre  mark  on  the  coffer  as  a  guide  for  fixing  it  fair  with 
the  centre  lines  on  the  soffit,  and  using  a  wood  square  to 
prove  the  square  of  the  style,  also  using  the  edge  of  the 
square  to  prove  the  level  of  the  coffer  with  the  run  sides 
of  the  soffit,  then  clean  off  any  excess  stuff  that  may 
exude  at  the  keyhole  and  edges  of  the  style.  After  this 
the  back  and  front  side  enrichments  are  fixed,  as  already 
mentioned.  Before  fixing  the  paterae  a  keyed  or  under- 
cut hole  must  be  cut  in  the  sunk  panels  to  give  a  key  for 
the  stuff  that  is  used  for  fixing  the  paterae.  A  corre- 
sponding keyed  hole  must  also  be  formed  on  the  back 
of  the  paterae.  This  is  best  done  by  making  the  desired 
size  of  sinking  in  the  model  of  the  paterae  before  it  is 
moulded.  These  sinkings  must  be  undercut  after  the  pa- 
terae are  cast. 

The  model  of  the  paterae  is  generally  moulded  with  a 
front  and  back  waxed  mould.  For  large  paterae,  or  those 
having  a  deep  projection  a  piece  of  twisted  galvanized 
or  copper  wire,  sufficiently  long  to  enter  the  keyed  holes 
in  the  paterae  and  the  soffit,  should  be  inserted  in  the 
fixing  stuff  when  fixing  the  paterae.  This  method  should 
always  be  adopted  where  the  bedding  surface  of  the  pa- 
terae is  small,  so  as  to  enable  it  to  resist  the  weight  of  a 
brush  while  being  painted  or  gilded.  If  the  paterae  are 
extra  deep,  and  project  below  the  line  of  the  soffit,  they 
should  be  fixed  first,  otherwise  they  are  liable  to  get  dis- 
turbed when  fixing  the  blocks  and  other  enrichments. 

The  modillions  should  be  fixed  with  stiff  gauged  stuff 
for  the  keyed  holes  in  the  styles,  and  the  corresponding 
holes  in  the  blocks  (which  are  made  while  being  cast), 
and  using  softer  gauged  stuff  for  the  bedding  surface  of 
the  block.    After  the  fixing  stuff  is  laid,  place  the  block 


152  CEMENTS  AND  CONCRETES 


in  position,  and  work  it  gently  but  quickly  from  right  to 
left,  so  as  to  force  the  excess  stuff  out,  and  obtain  a  true 
and  solid  bed,  taking  care  that  the  centre  of  the  block  is 
linable  with  the  centre  mark  on  the  soffit,  and  using  a 
square  to  prove  the  squareness  of  the  block,  and  then 
clean  off  the  excess  stuff.  The  small  enrichments  (Figs. 
6,  7,  and  10)  are  fixed  with  soft  gauged  stuff,  so  that 
they  can  be  easily  and  quickly  fixed.  Small  cast  work 
of  this  kind  should  always  be  fixed  with  soft  gauged 
stuff,  as  there  is  very  little  weight  to  carry  until  the  stuff  is 
set.  The  suction  alone  between  the  two  bodies  is  often  suf- 
ficient to  support  the  cast  until  the  stuff  is  set.  These  small 
enrichments  are  moulded  with  a  face  or  front  wax  mould. 


where  the  back  section  of  the  leaf  is  clear  or  away  from 
the  block  near  the  scroll  end,  as  shown  in  the  accom- 
panying illustration,  and  seen  in  fine  old  buildings,  th^ 
leaf  should  be  cast  and  fixed  separately.  An  enlarged 
view  of  the  plan  and  side  elevation  of  a  modillion  is 
shown  in  illustration  No.  5.  The  bed  moulds  and  the 
other  small  enrichments  in  the  entablature  are  generally 
cast  in  wax  moulds. 


Modillion. 
NO.  5. 


Modillions  or  blocks  were 
formerly  cast  in  three  parts, 
namely,  the  body,  the  main  part 
of  the  leaf,  and  the  tip  or  curled 
end  of  the  leaf;  the  body  being 
cast  in  a  wax  piece  mould  (some- 
times a  plaster  piece  mould) ,  and 
the  leaf  and  its  tip  in  a  front  and 
back  wax  mould,  but  now  the 
complete  block  is  generally  cast 
in  one  piece  in  a  gelatine  mould. 
The  body  of  the  block  may  be 
cast  in  a  gelatine  mould,  but 


TERMS  AND  PROCESSES  153 


"When  fixing  the  enrichments  in  an  entablature,  take 
special  care  that  they  all  principle"  with  each  other 
as  already  mentioned,  thus  forming  a  pleasing  and  artis- 
tic finish^  which  is  characteristic  of  well-designed  mould- 
ings. 


: 

\ 

u 

M 

Fig  2 

H  

3.  -f.- 

\ 

.      1  T 

m 

I     1  ',L 


'Corinthian  Cornice. 
NO.  6. 


To  Set  Out  a  Corinthian  Cornice, — The  members 
which  are  enriched  in  the  cornice,  shown  in  the  preced- 
ing plate,  are  drawn  as  plain  members  on  this  cornice  so 
as  to  show  the  profile  and  method  of  setting  out  more 
clear. 


154  CEMENTS  AND  CONCRETES 


The  combined  elevation  and  profile  of  the  cornice 
shown  at  Fig.  1,  in  the  accompanying  illnstration,  No.  6, 
is  an  enlarged  view  of  the  cornice  of  the  Corinthian  en- 
tablature. The  first  upright  scale  contains  four  parts  of 
the  ten  into  which  the  .whole  entablature  is  divided,  as 
on  the  preceding  plate.  The  second  scale  is  divided  into 
five  parts,  the  third  of  which  goes  to  the  modillion,  the 
fourth  to  the  corona,  and  fifth  to  the  cymatium ;  the  first 
and  second  together  are  divided  into  three  parts,  the  first 
for  the  reversed  cyma  at  the  bottom,  the  second  for  the 
dentils,  and  the  third  for  the  ovolo.  The  smaller  mem- 
bers are  in  proportion  to  the  greater,  as  shown  by  the 
smaller  divisions  on  the  scale.  The  modillions  are  1-6 
of  the  diameter  of  the  column,  and  their  distances  two- 
sixths  and  a  half.  Half  a  diameter  is  divided  on  the 
corona  at  Fig.  2  into  six  parts,  of  which  the  width  of  the 
modillion  is  two,  and  the  length  of  it  is  four.  The  cap 
projects  1-3  of  those  parts,  and  the  distance  between  the 
modillions  is  five.  By  this  rule  the  exact  distance  from 
centre  to  centre  of  the  modillions  is  7-12  of  the  diameter. 
The  dotted  line  A  C  answers  to  the  diminished  part  of 
the  coJumn,  from  whence  the  cornice  is  projected;  the 
projection  being  equal  to  its  height,  is  divided  into  four 
parts,  as  shown  by  the  scale  at  the  bottom  of  the  cor- 
nice. One-fourth  of  this  scale  is  divided  into  six  parts, 
as  shown  at  C,  five  of  which  gives  the  width  of  the  modil- 
lion. The  distance  between  them  is  in  proportion  to  it 
as  figured  at  Fig.  2.  The  fillets,  F  F,  of  the  modillion 
are  %  of  its  width,  and  so  is  the  bead,  B.  The  position 
and  size  of  the  sunk  panel  are  indicated  by  the  dotted 
lines  in  the  corona  at  Figs.  1  and  2,  the  size  being  ob- 
tained as  shown  by  the  figures  in  the  dotted  spaces.  The 
width  of  the  dentils,  D,  is  obtained  by  dividing  the  semi- 
diameter  of  the  column  marked  on  the  corona  at  Fig.  2 


TERMS  AND  PROCESSES  155 


into  fourteen  parts,  two  of  which  gives  the  width  of  the 
dentil,  and  one  the  space  between  them.  This  space  of 
course  is  also  the  width  of  the  in-dentil^  the  height  of 
which  is  one-fourth  of  the  height  of  the  main  dentil,  as 
indicated  by  the  small  division  on  the  inner  side  of  the 
second  upright  scale. 

The  centres  and  radius  for  describing  the  profiles  of 
the  cymatium  or  cymarecta,  the  ovolo,  and  the  inverted 
cyma  or  ogee  members  are  indicated  by  small  crosses  and 
dotted  lines. 

Mitring. — Mitring  is  looked  upon  by  the  generality  of 
plasterers  as  a  test  of  speed  and  ability.  As  they  gener- 
ally work  in  pairs  on  other  portions  of  the  work,  their  in- 
dividual ability  is  not  easily  seen,  but  when  mitring  a 
man  carries  the  operation  through  alone.  Mitring  being 
done  by  hand,  is  a  near  approach  to  modelling,  and  is  an 
operation  of  which  a  dexterous  and  good  plasterer  is  nat- 
urally proud.  The  quality  and  time  required  for  mitres 
greatly  depend  upon  the  degree  of  hardness  of  the  run 
cornice,  also  upon  the  suction.  A  mitre  can  be  more 
freely  worked  and  more  expeditiously  done  on  a  hard 
cornice  surface,  and  where  there  is  a  suction.  The  extra 
absorbing  powers  of  brick  walls  as  compared  to  lath  par- 
titions cause  the  gauged  stuff  to  get  firm  sooner,  and 
enables  the  mouldings  to  be  more  readily  blocked  out  be- 
fore the  stuff  is  set.  A  common  error  when  mitring  is 
gauging  the  stuff  stronger  than  that  which  has  been  used 
for  the  running  of  the  cornice,  causing  extra  swelling 
and  difficulty  of  ruling  the  members  over,  and  cutting 
the  run  part  of  the  cornice  with  the  joint  rule,  especially 
if  the  stuff  sets  before  the  plasterer  has  had  time  to  rule 
all  the  members  over,  and  then  being  stronger,  and  con- 
sequently setting  quicker,  he  has  not  so  much  time  for 
forming  the  members.    Ordinary  sized  mitres  can  be 


156  CEMENTS  AND  CONCRETES 


done  with  one  gauge  by  using  less  plaster  than  in  the 
gauge  for  running  the  cornice,  and  stiffening  the  greater 
portion  with  dry  plaster,  and  using  this  for  roughing  out 
the  mitre;  then  using  the  soft  portion  left  for  brushing 
over  the  members  and  filling  up  all  holes,  and  afterwards 
working  the  joint  rule  over  the  metal  to  take  the  su- 
perfluous stuff  off.  Should  the  mitre  not  be  fine  enough, 
the  gauged  stuff  can  be  further  softened  on  the  hawk  by 
adding  water,  and  working  it  with  the  gauging  trowel, 
brushing  the  soft  or  creamy  stuff  all  over  the  mitre 
again,  then  working  the  joint  rule  again.  Small  mem- 
bers, and  those  at  the  top  and  bottom  of  the  cornice, 
where  there  is  most  absorption,  should  be  worked  by  the 
joint  rule  first,  leaving  the  large  members,  drips  or  coves, 
or  where  there  is  a  large  body  of  stuff,  to  be  ruled  over 
last.  The  joint  rule  should  always  be  worked  horizon- 
tally, especially  when  dealing  with  beads  and  carvettos. 
Drips  and  large  members  should  be  worked  with  the 
joint  rule  with  an  upright  motion,  because  if  worked 
down,  the  stuff  may  be  pulled  down.  Mitres  should  not 
be  worked,  fined,  or  tooled  with  small  tools,  as  they  can 
and  should  be  brought  to  a  good  and  straight  surface 
by  the  proper  use  of  the  joint  rule.  Small  tools  should 
only  be  used  for  laying  the  stuff  when  required,  and 
cleaning  out  the  intersections  of  the  mitres,  quirks,  and 
for  stopping.  A  square-ended  small  tool  may  be  used 
for  smoothing  flat,  straight  surfaces.  Returned  mitres 
and  short  breaks  are  ^^run  down,''  then  cut  to  the  re- 
quired lengths  and  planted.  They  may  also  be  mitred 
by  hand. 

Mitre-Mould, — Various  attempts  have  been  made  to 
construct  a  running  mould  that  would  form  the  mitres 
simultaneously  with  the  cornice  running.  Most  plasterers 
will  have  heard  of,  and  some  may  have  tried  to  make 


TERMS  AND  PROCESSES  157 


and  work  a  mitre-mould  to  save  hand  labor.  Those  who 
have  tried  it  will  have  found  the  results  far  from  satis- 
factory. The  subjoined  illustration.  No.  7,  shows  the 
method  of  setting  out  and  constructing  a  mould  intended 


-Mitre-Mould. 
NO.  7. 


for  forming  the  moulding  and  mitres  in  one  operation. 
The  mould  is  made  by  fixing  the  metal  plate  at  an  angle 
of  45  degrees  on  the  slipper,  or  in  other  words  fixmg  the 
iron  plate  at  one  angle  of  a  square  slipper,  which  allows 
the  mould  to  run  nearly  up  to  the  angle,  one  face  of  the 
slipper  being  used  for  one  side  of  the  wall,  and  the  other 


158  CEMENTS  AND  CONCRETES 


face  at  right  angles  being  used  for  the  other  side  of  the 
wall.  Fig.  1  shows  the  method  of  setting  out  the  profile 
of  mould.  A  is  a  given  section  of  a  moulding,  and  B 
is  the  section  of  the  moulding  at  the  mitre.  To  obtain 
this,  first  draw  the  moulding  A  full  size,  and  then  extend 
the  ceiling  line  and  draw  another  wall  line.  Then  from 
the  projection  of  the  top  member  draw  an  angle  line  at 
45  degrees.  Carry  up  the  projections  of  the  various 
members  to  the  angle  (or  mitre  line)  and  then  draw  hori- 
zontal lines  from  the  various  members ;  also  centre  lines 
of  large  members  as  from  a  to  1  (the  vertical  letters). 
Take  off  the  lines  a  to  1  (diagonal  letters)  on  the  angle 
line,  and  set  them  on  the  ruling  line  from  a  to  1  (hori- 
zontal letters),  and  then  laying  them  down  to  the  hori- 
zontal lines,  the  intersections  give  the  profile  for  the 
mitre-mould.  Fig.  2  shows  a  side  elevation  of  the  mitre- 
mould,  and  Fig.  3  shows  a  front  elevation.  It  will  be 
seen  that  the  mitre-mould  is  an  expensive  and  unsatis- 
factory fad.  The  time  expended  in  setting  out  the  elon- 
gated members,  making  an  extra  mould,  and  cleaning 
out  the  intersection  by  hand  (as  the  mould  does  not  leave 
a  finished  mitre),  also  making  good  the  parts  broken  by 
drawing  out  the  mould  from  interlocked  or  undercut 
members  in  the  moulding,  is  not  repaid.  An  average 
plasterer  would  put  in  all  the  mitres  of  an  ordinary 
sized  room  while  the  mould  was  being  made.  The  mould 
will  only  run  into  every  second  angle,  and  must  be  taken 
off  and  reversed  to  fit  the  next.  It  may  seem  a  waste  of 
time  and  space  to  describe  and  then  show  the  utter  use- 
lessness  of  a  mitre-mould,  but  having  met  many  plas- 
terers who  stated  that  they  had  used  or  had  seen  a  mitre- 
mould  that  worked  wonders,  I  am  constrained  to  give  a 
description,  not  only  to  save  future  futile  controversy, 
but  to  show  that  in  this  book  the  much-debated  trade 


TERMS  AND  PROCESSES 


le59 


subject  has  not  been  omitted.  In  concluding  this  sub- 
ject, it  may  be  stated  that  not  any  one  of  the  mitre-mould 
plasterers  would  or  could  practically  explain  the  modus 
operandi  of  this  mysterious  mould. 

Fixing  Enrichments. — Enrichments  should  be  fixed 
straight,  square,  plumb,  and  firm.  Cornice  enrichments, 
such  as  bed  moulds,  friezes,  &c.,  for  which  a  bed  or  sink- 
ing to  receive  them  is  formed  by  the  running  mould,  do 
not  require  such  strong  gauges  stuff  as  soffits,  medallions, 
or  other  hanging  casts.  For  light  enrichments  the  gauged 
putty  and  plaster  should  never  be  stronger  than  that 
used  for  the  cornice,  and  clean  strong  size  water  should 
be  used.  This  gives  more  time  for  fixing  a  number  of 
casts,  and  improves  the  cementing  force.  The  bed  for 
the  cast  work  should  be  scratched,  dusted,  and  wetted 
before  the  cast  work  is  applied.  A  small  portion  of  fine 
plaster  (the  same  as  used  for  casting  the  enrichments) 
should  be  gauged  with  clean  size  water,  to  be  used  for 
the  joints.  The  gauged  fixing  stuff  should  be  spread 
evenly  over  the  back  of  the  cast  and  over  the  scratched 
bed  of  the  moulding.  No  more  should  be  laid  on  than 
will  fully  fill  up  the  scratches.  Then  place  a  small  piece 
of  the  white  or  joint  gauge  on  the  point,  and  press  the 
cast  into  position  by  gently  but  quickly  sliding  the  cast 
twice  or  thrice  backwards  and  forwards  to  expel  the  ^ir 
and  incorporate  the  two  bodies.  It  is  a  mistake  to  dab 
a  lump  of  gauged  stuff  at  random  on  the  back  of  the  cast 
and  press  it  on  the  bed,  as  the  stuff  does  not  properly 
enter  the  scratched  part  of  the  bed,  and  the  contained 
air  prevents  proper  cohesion  and  solidity.  When  too 
thick  a  coat  of  stuff  is  laid  on  the  coat,  straight  and  even 
fixing  is  more  difficult.  The  excess  stuff  oozes  out  at  the 
sides,  and  unless  time  and  care  be  taken  in  cleaning  it 
off,  the  moulding,  or  cast,  or  both,  get  damaged.  A 


160  CEMENTS  AND  CONCRETES 


small  portion  may  also  ooze  out  in  the  first  method,  but 
it  will  be  so  thin  that  it  can  be  brushed  off  while  soft. 
When  fixing  medallion  blocks  or  trusses,  a  dovetailed 
hole  should  be  cut  in  the  vertical  and  horizontal  parts  of 
the  bed,  and  similar  holes  in  the  blocks  (which  are  made 
when  being  cast)  are  filled  in  with  gauged  stuff  and 
applied  in  position.  If  the  cast  should  be  very  heavy, 
or  of  Portland  cement,  it  is  further  secured  by  inserting 
a  slate  or  iron  dowel  while  the  stuff  is  soft,  allowing  a 
portion  of  the  dowel  to  project  to  enter  into  the  body  of 
the  cast.  Heavy  casts  should  be  temporarily  supported 
by  wood  props  until  the  fixing  stuff  is  set.  When  fix- 
ing heavy  casts  the  plain  surface  of  the  plaster  work 
should  be  cut  as  far  as  the  lath  to  obtain  a  better  and 
stronger  key.  The  putty  in  the  fixing  stuff  should  be 
mixed  with  long  strong  hair  or  tow,  as  described  for  rib 
mouldings  or  ceilings.  Hair  or  tow  may  also  be  used 
advantageously  in  fixing  Portland  or  other  cement  work. 
Cast  work,  when  extremely  heavy,  should  be  further  se- 
cured by  means  of  long  screws  or  bolts,  placed  so  as  to 
pass  through  the  cast  work  and  into  the  timber,  the 
casts  being  bedded  with  gauged  haired  stuff  and  tem- 
porarily propped  up.  The  screws  or  bolts  should  be 
fixed  before  the  stuff  is  set  to  a^oid  the  probable  dis- 
turbance of  the  gauged  bedding.  Before  fixing  any  cast 
work  they  should  be  placed  in  position  to  prove  their 
correct  fitting.  Centre,  side  and  end  lines  should  be 
made  on  the  surface  of  the  bed  to  give  a  guide  for  fix- 
ing. It  may  be  necessary  to  fix  nails  at  intervals  in  the 
lines  to  give  a  further  guide. 

Mitring  Enrichments. — Before  fixing  continuous  or 
space  cast  work,  the  length  and  width  of  the  panel  or 
room  should  be  set  out  to  prove  that  the  mitres  are  equal- 
sided,  balanced  and  have  flowing  lines.    Nothing  lookfii 


TERMS  AND  PROCESSES 


161 


so  slovenly  or  unworkmanlike  as  a  mitre  in  an  ornament 
cut  haphazard,  with  the  leading  stem  disjointed  or 
springing  out  of  a  flower  or  tendril.  If  the  design  is 
vertical,  say  a  bed  mould  or  frieze  with  an  alternate  leaf 
and  husk,  what  can  be  more  offensive  to  artistic  taste 
than  a  part  of  the  leaf  on  one  side  and  a  part  of  the 
husk  on  the  other  side  of  the  mitre!  There  is  no  ex- 
cuse for  this  want  of  taste  and  wanton  treatment.  A 
little  time  expended  in  setting  out  the  work  will  obviate 
these  defects.  Where  there  are  no  shrinking  and  stretch- 
ing casts  the  mitres  can  be  eased  by  stretching  or  shrink- 
ing the  cast  work  at  the  joints.  Stretching  or  shrinking 
are  evils,  and  it  depends  on  the  design  of  the  enrich- 
ments which  of  the  two  is  the  lesser,  but  in  most  instances 
shrinking  is  the  greater  evil.  Shrinking  does  not  require 
so  much  labor  to  make  the  joints  good.  Stretching  does 
not  show  quite  so  much,  especially  if  the  joint  is  well 
modelled  and  of  the  same  color.  It  also  gives  greater 
scope  and  freedom.  It  has  already  been  mentioned  that 
in  good  shops  the  breaks  or  other  short  lengths  are  set 
out  in  the  shop  and  that  there  are  stretching  and  shrink- 
ing casts  and  mitres  modelled  and  made  to  facilitate  the 
formation  of  good  mitres.  This  latter  method  is  cer- 
tainly the  cheapest  and  most  satisfactory  in  the  end.  The 
setting  out  is  best  done  by  cutting  a  lath  as  a  gauge  to 
the  length  of  the  cast  and  marking  the  length  of  each 
cast  temporarily  on  the  bed  of  the  cast  work  from  mitre 
to  mitre.  When  the  mitre  has  been  determined  on  and 
the  casts  set  out  to  come  in,  the  marks  are  made  more 
distant  to  give  a  guide  for  fixing  each  separate  cast  as 
required.  It  is  better  to  measure  thrice  than  alter  twice. 
Space  ornaments  should  also  be  set  out  accurately,  but 
there  is  no  difficulty  in  the  mitres,  as  the  intervening 


162  CEMENTS  AND  CONCRETES 


space  between  each  cast  can  be  increased  or  diminished 
as  required. 

When  fixing  medallion  blocks^  dentils  or  paterae,  the 
mitres  should  be  fixed  first  and  then  the  spaces  and  posi- 
tions set  out.  Special  care  must  be  taken  when  mitring 
enrichments  with  distinctive  vertical  parts,  such  as  fig- 
ures, or  pendants  of  flowers,  or  fruit  in  friezes,  that  the 
cast  work  is  not  unequally  or  irregularly  scratched  so  as 
to  enable  them  to  come  to  an  equally  balanced  mitre  at 
the  angles.  Where  there  are  no  stretchers  the  cast  work 
should  be  cut  between  the  main  vertical  parts,  so  that  the 
joint  on  each  side  will  be  equal,  or,  in  other  words,  that 
the  vertical  parts  will  be  equidistant  from  the  main  or 
other  parts  when  fixed.  The  same  remarks  apply  to 
shrinking.  The  mitres  of  running  enrichments,  such  as 
soffits,  etc.,  are  made  up  with  bands  or  ribbons,  which 
are  cast  or  worked  in  situ  by  hand.  The  latter  way  is 
the  quickest  and  most  artistic.  Another  plan  is  to  fix 
paterae  or  drops  at  the  internal  and  external  mitres. 
The  scroll  work  of  the  enrichment  is  then  formed  to 
spring  from  the  paterae  and  finish  at  the  patera  at  the 
next  mitre.  Sometimes  the  inner  member  at  each  side 
of  the  soffit  is  worked  across  at  right  angles  at  each  mitre, 
thus  forming  a  sm.all  square  sinking  or  panel,  which  is 
then  filled  in  with  a  patera  or  drop. 

Bed  moulds,  such  as  an  egg  and  dart,  have  internal  and 
external  mitre  leaf  modelled  and  cast.  This  is  a  neat 
and  quick  way  of  forming  mitres.  A  good  cornice,  with 
well-modelled  and  effective  ornament,  may  be  disfigured 
and  spoiled  by  careless  mitring,  yet  it  is  as  easy  (and  in 
many  cases  more  so)  to  make  good  and  satisfactory 
work.  It  is  therefore  best  to  set  out  correctly  and  make 
sure  of  a  correct  finish  before  beginning  to  fix.  Illustra- 


TERMS  AND  PROCESSES  163 


tion  No.  8  shows  the  method  of  mitring  various  forms 
of  fret  enrichments. 

Pugging. — Pugging  or  deafening  is  a  body  of  plastic 
materials  laid  on  boards  fixed  between  the  joists  of  a 
floor,  or  lath  and  plaster  partitions.  It  is  intended  to 
prevent  sound  and  smells  from  passing  from  one  room 
to  another.  Pugging  is  generally  performed  by  laying 
a  thick  coat  of  coarse  stuff  on  a  foundation  of  rough 
boards  on  fillets,  which  are  nailed  on  the  sides  of  the 
joists.   Chopped  hay,  straw  or  ferns,  mixed  with  lime,  is 


^Fret  Or.n'aments.  showing  their  Mitres. 
NO.  8. 


sometimes  used  for  the  plastic  coat.  Coarse  plaster  with 
and  without  reeds  is  also  used  in  some  districts.  Saw- 
dust is  sometimes  substituted  for  reeds.  Pugging  may 
be  done  by  forming  a  foundation  with  thick  rough  lath 
wood.  On  this  a  coat,  about  ^2  i^ch  thick,  of  coarse  stuff 
is  laid,  and  when  dry  a  layer  about  2  inches  thick  of  dry 
ashes  or  lime  riddlings  is  deposited  on  it.  The  upper  sur- 
face is  then  sprinkled  with  water  and  finished  with  a  coat 
of  coarse  stuff.  This  makes  sound-proof  work,  but  in  the 


164  CEMENTS  AND  CONCRETES 


event  of  subsequent  damage  or  alterations  the  dry  ashes 
run  out,  causing  further  dust  and  damage.  In  some  in- 
stances the  dry  ashes  are  gauged  with  lime.  When  laid 
the  upper  surface  is  beaten  and  smoothed  with  a  shovel. 
This  makes  sound-proof  and  durable  work,  impervious  to 
vermin.  Partitions  are  deafened  by  lathing  between 
the  studding  and  then  laying  on  a  coat  of  coarse  stuff. 
When  dry  the  partition  is  lathed  and  plastered  in  the 
usual  way.  Pugging  slabs  of  fibrous  plaster  are  now 
largely  employed.  They  have  the  advantage  of  being 
light  and  dry  and  are  rapidly  fixed. 

Sound  Ceilings. — No  lath  and  plaster  ceilings  can  be 
made  sound  and  free  from  cracks  unless  the  joists  are 
well  seasoned,  firmly  fixed  and  sufficiently  strong  to 
carry  the  overhead  weight,  as  well  as  sustain  the  weight 
of  the  lath  and  plaster,  and  resist  jarring.  Ceiling  joists 
should  never  be  more  than  12  inches  apart  from  center 
to  center.  Where  double  lath  is  used  the  joists  may  be 
14  inches  from  center  to  center.  Good  laths,  with  break 
joints  every  three  feet,  and  well  nailed,  are  also  impera- 
tive. If  the  above  dimensions  are  exceeded  the  laths 
are  liable  to  give  or  twist  on  account  of  the  weakness  of 
the  laths  or  the  weight  of  the  plaster,  or  both  com- 
bined. If  the  joists  exceed  2  inches  in  the  width  they 
should  be  counter-lathed  or  strapped  to  ensure  a  key  for 
the  plaster.  Where  it  is  impracticable  or  inconvenient 
to  fix  the  ceiling  joists  so  close  they  should  be  brand- 
ered.  This  strengthens  and  stiffens  the  joists,  also  gives 
a  free  key  for  the  plaster  and  forms  a  sound,  level  ceil- 
ing. 

Brandered  or  strapped  ceilings  are  done  by  nailing 
wood  straps  or  fillets  across  the  under  sides  of  the  joists. 
The  fillets  are  from  1^^  to  2  inches  square  and  are  fixed 
from  12  to  14  inches  from  centre  to  centre.    The  sizes 


TERMS  AND  PROCESSES  165 


and  distance  apart  varies  according  to  the  thickness  of 
the  lath  and  the  class  of  plaster  work.  Brandered  ceil- 
ings are  largely  used  in  some  places  and  make  good 
sound  ceilings. 

Cracked  Plaster  Work. — Cracks  in  plaster  work  are 
due  to  various  causes.  They  may  act  individually  or  in 
combination.  Cracks  are  often  caused  by  settlement  in 
the  building.  These  cracks  may  be  easily  discerned  by 
their  breadth,  depth  and  length.  They  also  arise  from 
the  shrinkage  of  bad  or  unseasoned  timber  used  in  the 
construction  or  framing  of  the  building,  which  may 
cause  displacement  in  the  joists  or  the  laths.  Cracks 
are  sometimes  caused  by  the  laths  being  too  weak,  or  by 
too  much  plaster  being  laid  on  weak  laths,  or  too  little 
plaster  laid  on  strong  laths.  Other  causes  are  the  too 
sudden  drying  of  the  work,  strong  winds  or  heat,  ihe 
laying  of  one  coat  of  mortar  on  another  coat,  or  on  walls 
that  have  a  strong  suction  which  absorbs  the  moisture  or 
'4ife"  of  the  coat  being  laid,  when  it  becomes  short,  or 
crumbly,  scaly  and  apt  to  peel  or  fall  off.  In  this  last 
case  it  does  not  set,  but  only  dries  and  shrinks,  which 
gives  rise  to  cracks,  and  eventually  falls  or  crumbles 
away.  The  use  of  bad  materials,  insufficient  use  of  lime 
and  hair,  or  scamping  of  labor  is  often  followed  by 
cracks.  Insufficient  labor  and  unskilled  workmanship  in 
the  application  of  the  materials  is  a  great  source  of 
trouble,  but  it  will  be  understood  that  the  best  quality 
of  labor  will  not  make  bad  materials  good  and  strong; 
and,  on  the  other  hand,  the  best  materials  will  not  com- 
pensate for  bad  labor.  It  is  only  by  judicious  selection 
of  materials  and  their  skillful  manipulation  that  a  high 
and  enduring  class  of  work  can  be  obtained. 

Repairing  Old  Plaster. — Repairing  is  also  termed 
'^patching,"  ''jobbing"  and  ''making  good."  "When 


166  CEMENTS  AND  CONCRETES 


repairing  or  making  additions  to  old  plaster  work,  care 
should  be  observed  in  cutting  the  joints  so  that  the  key  of 
the  existing  work  is  not  injured  or  broken.  The  joints 
one  way  should  be  cut  on  the  studding  or  joists  and  in 
a  line  with  the  laths  the  other  way.  A  joint  at  the  edge 
of  a  lath  is  stronger  than  at  the  center.  If  the  lath  work 
is  weak  the  joints  should  be  cut  diagonally.  Never  use 
a  hammer  to  cut  joints  on  lath  work,  for  the  repeated  im- 
pacts will  weaken  and  crack  the  old  work.  If  the  old 
plaster  is  hard,  cut  the  joint  with  the  saw  or  with  a  ham- 
mer and  chisel  and  finish  with  a  strong  knife.  Avoid 
acute  angles  in  patches.  Square,  round  or  oval  patches 
not  only  look  better  but  are  much  stronger  than  zigzag 
ones.  Having  cut  the  joints  neat  and  square  on  edge 
and  then  repaired  the  old  lath  work,  brush  the  joints 
and  the  laths  with  a  dry  broom  and  then  wet  the  joints, 
but  only  dampen  the  lath  work,  as  excessive  water  tends 
to  warp  the  laths.  The  joints  are  sometimes  painted  to 
prevent  damp  from  extending  to  the  old  work  or  caus- 
ing injury  to  any  surface  decoration.  Gauged  coarse 
stuff  is  generally  used  for  roughing  out  and  gauged  putty 
for  finishing  ordinary  work.  The  coarse  stuff  is  gen- 
erally gauged  with  coarse  plaster.  For  small  patches 
the  whole  thickness  is  generally  brought  out  in  one  coat, 
but  for  large  patches  it  is  best  to  lay  a  first  coat  and 
then  scratch  it  in  the  usual  way.  If  time  permits  this 
should  stand  for  one  day,  or  even  two,  to  allow  the  lath 
work  to  settle.  The  stronger  and  stiffer  the  gauge,  the 
less  power  the  laths  will  have  to  warp.  The  floating  coat 
is  gauged  moderately  stiff  with  coarse  plaster  or  with 
fine  plaster  and  coarse  in  equal  proportions. 

When  laid,  the  surface  is  ruled  in  with  a  straight- 
edge, keeping  it  within  the  line  of  the  old  work  to  allow 
for  plaster  swelling  and  a  thickness  of  1-16  inch  for  the 


TERMS  AND  PROCESSES  167 


finishing  coat.  It  is  often  necessary  to  drag  the  surface 
down  to  allow  the  finishing  coat  to  be  ruled  fair  and 
flush  with  the  old  work.  The  surface  should  be  left  fair 
but  rough.  Gauged  work  should  never  be  scoured,  as  it 
only  kills  the  plaster,  and  therefore  weakens  the  body  of 
the  material.  The  putty  for  the  final  coat  should  be 
gauged  with  fine  plaster  and  a  little  size  water.  After 
being  laid  the  surface  is  ruled  flush  with  the  old  work, 
and  when  firm  it  should  be  smartly  trowelled  off  and 
finally  finished  with  a  semi-wet  brush.  The  joints  should 
be  trowelled  flush  and  smooth  and  the  old  part  brushed 
to  free  it  from  any  gauged  stuff.  All  rubbish  should  be 
damped  as  it  falls,  and  removed  as  soon  as  possible  to 
prevent  further  dust  and  dirt. 

Parian  or  other  white  cements  are  used  for  best  work, 
or  where  time  is  a  consideration.  All  white  cements 
having  plaster  for  their  basis  are  manufactured  to  be 
non-efflorescent,  non-porous,  durable,  free  from  liability 
to  unequal  shrinkage  (which  causes  cracks),  and  free  in 
working.  They  form  admirable  materials  for  repairs  or 
additions.  When  making  good  old  or  broken  lime  plaster 
work  with  any  of  these  cements,  the  joints  and  lath  nails 
must  be  painted  with  red  lead,  quick  drying  paint,  or 
with  shellac.  Galvanized  nails  ought  to  be  used  for  the 
lath  work  where  these  cements  are  to  be  used.  Small  holes 
and  cracks  are  usually  stopped  with  fine  plaster  gauged 
with  putty,  or  better  still,  putty  water.  Parian  cement  is 
also  used  for  a  similar  purpose.  The  holes  and  cracks 
should  be  brushed  with  Parian  solution  before  the  stiff 
Parian  is  applied.  This  solution  is  simply  fine  Parian 
gauged  to  a  thin  creamy  consistency  with  water.  New  or 
damp  lime-plastered  walls  can  be  painted  or  papered 
much  sooner,  and  with  greater  safety,  if  brushed  with  a 
thin  Parian  solution.  It  is  also  useful  for  stopping  the 


168  CEMENTS  AND  CONCRETES 


suction  on  dry  floating  and  fibrous  slabs  before  laying 
the  final  coat.  Several  of  the  new  patent  plaster  and 
white  cements  are  well  adapted  for  repairs,  or  where 
time  is  limited. 

Gauged  Work. — All  gauged  work  should  be  regulated 
in  strength  according  to  the  purpose  required.  A  brick 
or  stone  wall  would  not  require  so  much  plaster  as  a  lath 
partition.  Work  not  subject  to  friction  or  wear  does  not 
require  so  much  plaster.  If  the  work  is  required  for 
immediate  use,  as  with  running  screeds,  or  blocking  out 
large  mouldings,  or  fixing  large  castings  much  plaster 
must  be  used.  The  amount  of  plaster  required  for  scaf- 
fold work  varies  from  ^  to  equal  proportions  for  gaug- 
ing coarse  stuff  or  setting  stuff,  and  from  1-3  to  equal 
proportions  for  coarse  stuff  for  heavy  cornices,  and  1-3 
to  equal  proportions  for  putty  and  fixing  ornament.  The 
amount  of  plaster  also  depends  upon  the  quality  of  the 
plaster,  some  of  which  are  much  stronger  than  others. 
Coarse  plaster  that  is  of  a  dark  and  sandy  nature  is  gen- 
erally weak,  sets  quickly,  and  becomes  soft  and  useless. 
Fine  plaster  should  be  used  for  gauging  putty  when  run- 
ning cornices,  also  for  fixing  enrichments.  All  gauged 
work  should  be  gauged  with  uniformity,  each  separate 
gauge  having  the  same  amount  of  water  and  plaster  as 
required  for  the  bulk  of  stuff  being  gauged.  Unequal 
gauging  causes  hard  and  soft  places  in  the  work,  and 
when  more  plaster  is  used  in  one  gauge  than  another 
there  is  an  extra  expansion  caused  by  the  swelling  of 
the  plaster,  which  makes  the  work  more  difficult  to  do 
when  floating,  setting,  runn,ing  mouldings,  or  mitring. 

A  quart  and  a  pint  measure  should  always  be  kept  on 
the  scaffold  for  measuring  the  water  used  for  the  vari- 
ous gauges.  The  quantity  of  water  will  regulate  the 
quantity  of  plaster  for  each  gauge.    A  proper  plaster 


TERMS  AND  PROCESSES 


169 


box  should  also  be  on  the  scaffold,  made  to  hold  a  sack  of 
plaster,  and  having  a  lid  made  in  two  halves  hinged  from 
the  centre.  This  prevents  the  plaster  from  getting  dirty 
by  falling  stuff,  and  from  getting  damp  by  absorption 
from  the  atmosphere.  Where  there  is  a  large  quantity 
or  continuous  gauging,  the  box  should  be  placed  on  a 
stand  (this  is  called  a  stand-box)  to  prevent  unnecessary 
exertion  and  loss  of  time  by  stooping  for  each  handful. 

When  gauging  coarse  stuff  for  large  surfaces  which 
require  several  gauges  to  complete  the  work  in  hand,  size 
w^ater  should  be  used  in  proper  proportions  with  the  neat 
water  used  for  gauging,  so  as  to  allow  sufficient  time  to 
properly  manipulate  the  material.  In  the  event  of 
gauged  stuff  setting  before  the  work  is  laid  and  ruled  off, 
it  is  difficult  to  make  the  surface  strong  and  fair.  This 
also  allows  the  various  gauges  to  be  laid  on  or  against 
the  previous  ones  while  they  are  in  a  soft  state^  thus 
forming  stronger  joints  and  better  cohesion  between  the 
various  gauges.  The  use  of  size  water  in  gauged  set- 
ting stuff  and  putty  enables  the  work  to  be  freely  trow- 
elled and  finished.  Gauged  stuff  should  not  be  hand- 
floated,  as  excessive  working  destroys  the  setting  powers 
of  the  plaster. 

Joist  Lines  on  Ceilings. — Common  flat  ceilings  show 
in  time  the  precise  position  of  the  joists  above,  and  in 
many  instances  the  position  and  form  of  the  lath  work 
can  be  easily  discerned.  Many  theories  have  been  ad- 
vanced as  to  the  cause  of  these  unsightly  lines  or  marks, 
which  are  so  distressing  to  the  mind  and  eye.  In  my 
opinion  they  are  due  in  a  great  measure  to  insufficient 
material  and  inferior  work.  The  plaster  which  is  be- 
tween or  separate  from  the  joists  is  more  pervious  to  the 
atmosphere  than  that  which  is  in  more  direct  contact. 
The  air  in  passing  through  leaves  behind  it  particles  of 


170  CEMENTS  AND  CONCRETES 

dirt  assigned  in  larger  measure  to  the  unattached  than 
to  the  attached  portions.  Dust  that  finds  ingress  be- 
tween the  joints  of  flooring  boards  lies  on  the  unattached 
portions,  consequently  the  joists  show  themselves  as 
lighter  lines  on  a  more  or  less  dirty  background.  The 
same  causes  apply  to  the  lines  on  the  lath  work.  An- 
other cause  is  that  the  plaster  work  is  too  thin.  In  many 
instances  the  floating  is  brought  up  from  the  lath  in  one 
coat.-  This  is  a  most  pernicious  habit,  as  it  is  not  only 
the  cause  of  lath  lines,  but  the  ceiling  invariably  cracks, 
and  develops  spontaneously  original  patterns  indicative 
of  rivers,  which  too  often  lead  like  Niagara  to  a  catas- 
trophe in  the  form  of  falling  plaster.  Joists  and  lath 
lines  on  thin  ceilings  may  be  partly  obviated  by  laying 
strong  brown  paper  over  the  upper  side  of  the  lath  and 
plaster  and  then  pasting  the  edges  to  the  sides  of  the 
joists,  so  as  to  form  a  cover  to  the  plaster  work.  The 
better  and  most  sanitary  way  is  to  lay  the  work  in  three 
coats,  allow^  the  first  coat  to  dry,  consolidate  the  floating 
coat  by  well  scouring  with  a  hand  float,  and  render  the 
setting  coat  hard,  non-absorbent,  and  impervious  to  the 
air  by  thorough  scouring,  trowelling,  and  brushing. 

Rough  Casting. 

Several  years  ago  I  was  requested  by  the  Editor  of 
'^Architecture  and  Building''  of  New  York  to  prepare  a 
short  treatise  on  the  subject  of  Rough  Casting"  for 
publication  in  that  magazine.  The  article  was  pub- 
lished in  almost  every  architectural  journal  in  the  coun- 
try, and  Mr.  Kidder  embodied  it  in  his  excellent  work. 

Building  Construction  and  Superintendence,  Vol.  I." 
I  reproduce  it  here,  as  the  directions  given  therein  have 
been  found  to  be  of  the  very  best,  and  most  workmen  in 


TERMS  AND  PROCESSES 


this  line  of  the  trade  adopt  the  methods  of  manipulation 
herein  described. 

Rough  casting,  or,  as  it  is  sometimes  called,  slap 
dashing,  both  of  which  are  synonymous  with  the  French 
Jiourdage,  rough  work,  and  ravalement,  having  a  similar 
meaning,  is  a  method  of  plastering  the  outside  of  a  build- 
ing much  used  in  the  northern  part  of  -Canada  because 
of  its  being  durable,  cheap  and  well  adapted  to  keep  out 
cold  winds  during  the  long  winters  in  that  section  of 
the  world.  The  methods  of  applying  rough  cast  and  the 
mixing  thereof'  do  not  materially  differ  from  the  meth- 
ods adopted  in  Northern  Europe  or  even  in  the  North- 
western States,  but  it  is  these  minor  differences,  says  a 
writer  in  an  exchange,  that  make  the  Canadian  rough 
casting  superior,  so  far  as  durability  is  concerned,  to 
much  that  is  done  in  other  parts  of  the  world. 

There  are  frame  cottages  near  the  City  of  Toronto  and 
along  the  northern  shores  of  Lake  Ontario  that  were 
plastered  and  roughcasted  exteriorly  over  40  years  ago, 
and  the  mortar  today  is  as  good  and  sound  as  when 
first  put  on,  and  it  looks  as  though  it  was  good  for  many 
years  yet  if  the  timbers  of  the  building  it  preserves  re- 
main good.  Rough  cast  buildings  are  plentiful  in  every 
province  in  the  Dominion  from  Halifax  to  Vancouver 
and  from  Lake  Erie  to  Hudson  Bay,  and  when  well  built 
and  the  rough  cast  properly  mixed  and  properly  applied 
the  result  is  always  satisfactory.  It  is  quite  a  common 
occurrence  in  Manitoba  and  the  Northwest  Territories 
in  the  winter  to  find  the  mercury  frozen,  yet  this  inten- 
sity of  frost  does  not  seem  to  affect  the  rough  casting  in 
the  least,  though  it  will  chip  bricks,  contract  and  expand 
timber,  and  render  stone  as  brittle  as  glass  in  many 
cases,  and  the  effect  on  iron  and  steel  is  such  as  may 


172  CEMENTS  AND  CONCRETES 


prove  dangerous  if  exposed  to  sudden  and  unexpected 
strain. 

In  preparing  a  frame  or  log  building  for  rough  cast- 
ing care  must  be  taken  in  putting  down  the  founda- 
tion. A  good  stone  or  brick  foundation  is,  of  course,  the 
best,  but  where  rough  casting  is  intended  stone  or  brick 
foundations  are  seldom  used  because  of  their  cost,  and 
the  builder  is  compelled  to-  use  posts  of  wood.  The 
posts  are  generally  made  of  white  cedar,  which  has  a 
lasting  quality  of  35  or  40  years  if  sound  when  used. 
The  posts  are  put  in  the  ground  from  3  to  5  feet,  the 
deeper  the  better,  as  they  should  be  deep  enough  in  any 
case  to  prevent  frost  from  forcing  them  upward.  When 
a  suflicient  number  of  posts  have  been  properly  placed 
a  line  is  struck  on  them  a  proper  height  from  the  ground 
and  the  tops  levelled  off.  The  sills  are  then  placed — all 
joints  being  broken  on  top  of  posts — and  the  whole  made 
level.  These  sills  and  all  the  other  timber,  scantlings 
and  lumber  should  be  well  seasoned,  if  possible,  for  the 
greatest  enemy  to  the  plasterer  is  unseasoned  timber; 
shrinkage  of  joists,  posts  and  scantling  not  only  breaks 
the  bond  of  the  mortar,  but  causes  great  cracks  in  cor- 
ners and  angles  that  no  amount  of  pointing  or  patching 
can  ever  make  good. 

When  the  frame  is  up  and  the  rafter  on  and  well  se- 
cured the  whole  of  the  outside  should  be  covered  with 
good,  sound,  common  inch  stock  pine,  hemlock,  spruce, 
or  other  suitable  lumber,  dressed  to  a  thickness.  If  put 
on  diagonally  so  much  the  better,  but  this  is  not  abso- 
lutely necessary  if  the  rough  casting  is  to  be  of  the  best 
quality,  as  will  appear  hereafter. 

When  it  can  be  done  it  is  best  to  get  all  partitions  set 
in  place  and  lathed,  the  roof  on  and  all  necessary  out- 
side finish  or  grounds  put  in  place  and  made  ready  to 


TERMS  AND  PROCESSES 


173 


receive  the  lath.  The  carpenter  must  prepare  his  finish 
or  grounds  for  finish  to  accommodate  the  extra  lath,  as 
the  walls  will  be  thickened  accordingly. 

For  the  cheaper  sort  of  rough  casting  in  one  or  two 
coats  the  following  method  of  lathing  is  employed:  Nail 
laths  on  the  boarding — over  paper  or  felt,  if  paper  or 
felt  is  used — perpendicularly  16  inches  from  centre  to 
centre  if  4  foot  laths  are  used,  or  18  inches  or  1  foot 
from  center  to  center  if  3  foot  laths  are  used.  The  whole 
surface  to  be  rough  cast  will  require  lathing  this  way. 
When  done  lath  as  is  ordinarily  done  with  No.  1  pine 
lath,  breaking  joints  every  15  inches.  Put  5  nails  in 
each  lath,  driving  each  nail  home  solid,  coat  over  w^ith 
mortar,  well  haired,  and  that  has  been  made  four  or  more 
days;  smooth  and  straighten  as  well  as  possible  with  a 
darby.  When  done  and  while  yet  soft  tlie  rough  cast  is 
thrown  on  it  with  such  force  as  to  drive  the  pebbles  or 
small  stones  deep  into  it.  The  mixture  or  dash,  as  it  is 
called,  is  composed  of  fine  gravel,  clean  washed  from  all 
earthy  particles  and  mixed  with  pure  lime  and  water 
till  the  whole  is  of  a  semi-fluid  consistency.  This  is 
mixed  in  a  shallow  tub  or  pail  and  is  thrown  upon  the 
plastered  wall  with  a  wooden  float  about  5  or  6  inches 
long  and  as  many  wide,  made  of  inch  pine,  and  fitted 
with  a  wooden  handle.  While  with  this  tool  the  plaster- 
er throws  on  the  rough  cast  with  his  right  hand,  he  holds 
in  his  left  a  common  white-wash  brush,  which  he  dips 
into  the  rough  cast  and  then  brushes  over  the  mortar 
and  rough  cast,  which  gives  them,  when  finished,  a  reg- 
ular, uniform  color  and  appearance. 

For  this  sort  of  work  the  following  proportions  will 
answer :  To  one  barrel  of  prepared  gravel  use  a  quarter 
of  a  barrel  of  putty;  mix  well  before  using.  This  may 
be  colored  to  suit  the  taste  by  using  the  proper  materials, 


174  CEMENTS  AND  CONCRETES 


as  given  further  on.  It  must  be  understood  that  the  fore- 
going is  the  cheapest  sort  of  rough  casting,  and  is  not 
recommended  where  more  durable  but  more  expensive 
work  is  required. 

The  best  mode  of  doing  this  work  as  practised  in  the 
Lake  district  of  Ontario  is  nearly  as  follows.  Have  the 
frame  of  building  prepared  as  indicated  in  the  foregoing, 
with  partitions  all  put  in  and  well  braced  throughout  and 
well  secured.  Lath  diagonally  with  No.  1  pine  lath, 
keeping  IV2  inches  space  between  the  lath.  Nail  each 
lath  with  5  nails,  and  break  joints  every  eighteen  inches. 
Over  this  lath  again  diagonally  in  the  opposite  direction, 
keeping  the  same  space  between  the  lath  and  breaking 
joints  as  before.  Careful  and  solid  nailing  is  required 
for  this  layer  of  lathing,  as  the  permanency  of  the  work 
depends  to  some  extent  on  this  portion  of  it  being  honest- 
ly done.  The  mortar  used  for  the  first  coat  should  have 
a  goodly  supply  of  cow's  hair  mixed  in  with  it,  and 
should  be  made  at  least  four  days  before  using.  The 
operator  must  see  to  it  that  the  mortar  be  well  pressed 
into  the  key  or  interstices  of  the  lathing  to  make  it 
hold  good.  The  face  of  the  work  must  be  well  scratched 
to  form  a  key  for  the  second  coat,  which  must  not  be  put 
on  before  the  first  or  scratch  coat  is  dry.  The  mortar  for 
the  second  coat  is  made  in  the  same  way  as  that  re- 
quired for  the  first  coat,  and  is  applied  in  a  similar  man- 
ner, with  the  exception  that  the  scratch  coat  must  be 
well  damped  before  the  second  coat  is  put  on  in  order 
to  keep  the  second  coat  moist  and  soft  until  the  dash  or 
rough  cast  is  thrown  in.  The  rough  casting  is  done  ex- 
actly in  the  same  manner  as  described  for  the  cheaper 
sort  of  rough  cast  work. 

A  building  finished  in  this  manner,  if  the  work  is  well 
done,  possesses  many  advantages  over  the  ordinary 


TERMS  AND  PROCESSES  175 


wood  coyered  structure.  It  is  much  warmer  being  al- 
most air  tight  so  far  as  the  walls  are  concerned.  It  is 
safer,  as  fire  will  not  eat  its  way  through  work  of  that 
kind  for  a  long  time.  It  is  cleaner,  as  it  will  not  prove 
such  a  harbor  for  insects.  It  may  be  made  as  handsome 
as  desired,  for  before  the  rough  cast  is  dashed  it  may  be 
laid  off  in  panels  of  any  shape  by  having  strips  of  bat- 
tens tacked  over  the  soft  mortar,  which  may  be  removed 
after  the  rough  casting  is  done  and  the  coloring  finished. 
It  is  much  superior  to  the  so-called  brick  veneered  house, 
as  it  is  warmer,  more  exempt  from  fire  and  cheaper. 

For  100  yards  of  rough  casting  in  the  manner 
described  the  following  quantities  will  be  required:  1800 
laths,  12  bushels  of  lime,  li/^  barrels  of  best  cow  hair, 
1%  yards  of  sand,  %  yard  of  prepared  gravel  and  16 
pounds  of  hot  cut  lath  nails,  1^/4  inches  long.  The  gravel 
should  be  sifted  through  a  i/^  inch  mesh  screen,  and 
should  be  washed  before  mixing  with  the  lime  putty. 

To  color  100  yards  in  any  of  the  tints  named  herewith 
use  the  following  quantities  of  ingredients :  For  a  blue 
black  mix  5  pounds  of  lamp  black  in  the  dash.  For  a 
buff  use  5  pounds  of  green  copperas,  to  which  add  1 
pound  of  fresh  cow  manure ;  strain  all  and  mix  well  with 
the  dash.  A  fine  terra  cotta  is  made  by  using  15  pounds 
of  metallic  oxide  mixed  with  5  pounds  of  green  copperas. 
A  dark  green  color  is  made  by  using  5  pounds  of  green 
copperas  and  4  pounds  of  lamp  black.  Many  tints  of 
these  colors  may  be  obtained  by  varying  the  quantities 
given.  The  colors  obtained  by  these  methods  are  perma- 
nent; they  do  not  fade  or  change  with  time  or  atmos- 
pheric variations.  Many  other  colors  are  used  but  few 
stand  like  the  ones  named.  A  brick  color  may  be  obtained 
by  the  use  of  Venetian  red  and  umber  mixed  in  whisky 
first  and  then  poured  into  the  dash  until  the  proper  tint 


176 


CEMENTS  AND  CONCRETES 


is  obtained.  In  time,  however,  like  all  earthy  pig- 
ments, these  colors  fade  and  have  a  sickly  appearance; 
they  answer  better  in  cements  than  when  incorporated 
with  fat  limes. 


VARIOUS  METHODS  OF  RUNNING  CORNICES, 
CIRCLES,  ELLIPSES  AND  OTHER  ORNAMEN- 
TAL STUCCO  WORK. 

Diminished  Columns. — The  diminishing  of  columns  is 
an  interesting  but  somewhat  difficult  operation.  Great 
care  must  be  exercised  not  to  overdo  the  entasis  or  swell- 
ing. The  swell  may  commence  very  gradually  from  the 
base  to  the  capital,  or  the  third  part  of  the  column  may 
be  of  the  same  diameter,  and  then  swell  and  diminish  for 
the  remainder  of  its  height.  Two  methods  are  here  given 
to  show  how  this  may  be  done.  These  are  given  more 
to  illustrate  the  method  of  setting  out  the  diminished 
floating  rulesi — so  necessary  to  the  plasterer — than  to 
define  the  iswell  or  diminishing  of  a  column,  which,  being 
within  limits  a  matter  of  taste,  pertains  more  correctly 
to  the  architect. 

The  best  instrument  for  forming  a  diminished  column 
(plain  or  fluted)  is  a  diminished  floating  rule,  with  a 
cutting  edge  made  to  the  contour  of  the  proposed  col- 
umn. This  rule  is  used  to  determine  the  central  posi- 
tion of  the  astragal  and  base  mouldings  (which  act  as 
bearings  when  ruling  off  the  floating  stuff'  and  the  final 
coat),  so  as  to  obtain  a  true  and  uniform  diminish,  and 
also  to  form  a  fair  surface.  The  appended  illustration 
No.  9  elucidates  the  method  of  setting  out  diminished 
columns  which  is  also  used  for  setting  out  the  diminished 
rule  for  both  columns.  The  method  for  setting  out  a 
diminished  rule  for  a  column  that  diminishes  two  thirds 
of  its  height  is  as  follows :  The  dimensions  of  the  column 

177 


METHODS  OF  WORK 


179 


having  been  fixed,  i.  e.,  the  height  of  the  shaft  and  itiS 
upper  and  lower  diameters,  draw  a  perpendicular  line 
which  may  be  taken  as  the  centre  line  of  the  column; 
then  set  out  the  upper  and  lower  diameters,  as  shown  in 
Fig.  la.  This  figure  also  shows  one-half  of  the  eon- 
structural  brick  work,  and  the  plaster,  which  is  dis- 
tinguished by  being  dark  shaded  with  the  floating  rule 
in  position.  A  floating  rule  for  forming  the  curved  and 
diminished  surface  requires  an  iron  plate,  similar  to  a 
mould  plate,  as  shown,  so  that  it  will  cut  the  stuff  off 
cleaner  and  truer,  and  last  longer.  The  other  half  of  the 
elevation  shows  the  lines  and  divisions  for  obtaining  and 
setting  out  the  entasis. 

To  diminish  the  column,  first  divide  the  height  into 
three  equal  parts  then  at  the  lower  third  (5)  draw  a 
semicircle  equal  to  the  lower  diameter  of  the  column. 
Next  divide  the  upper  portion  of  the  column  into  four 
equal  parts,  as -shown  at  1,  2,  3  and  4,  then  draw  a  line, 
parallel  with  the  axis  or  centre  line  of  the  column,  from 
figure  1  at  the  top  of  the  column,  cutting  the  semicircle 
at  1,  divide  the  remainder  of  the  semicircle  into  four 
equal  parts,  w^hich  gives  the  diminishing  points.  From 
these  points  draw  lines  parallel  to  the  axis  of  the  column, 
and  from  the  corresponding  figures,  or  from  2  to  2,  and 
so  on.  In  these  intersecting  points  fix  pins  or  nails,  and 
bend  a  flexible  strip  of  wood  or  metal  round  the  nails, 
and  draw  the  curved  line.  The  whole  line  from  top  to 
bottom  is  then,  transferred  on  to  the  board  that  is  to  be 
used  for  making  the  floating  rule.  This  column  will  have 
its  greatest  diameter  for  one-third  of  its  height,  and  the 
upper  portion  its  entasis.  This  method  is  so  far  defect- 
ive as  to  require  the  curve  to  be  drawn  by  hand,  a  de- 
fect, however,  obviated  by  using  a  column  trammel, 
which  is  used  for  a  column  that  diminishes  with  a  grace- 


180  CEMENTS  AND  CONCRETES 


ful  curve  from  the  base  to  top  of  the  shaft.  This  tramme] 
is  made  as  follows: 

Column  Trammel. — A  column  trammel  is  simple  in 
construction,  and  when  carefully  used  gives  very  satis- 
factory results^  forming  a  graceful  diminished  curve 
from  the  lower  diameter  to  the  upper  diameter  of  the 
shaft.  Before  describing  the  method  of  setting  out  and 
constructing  the  column  trammel,  the  method  of  finding 
the  point  D  on  Fig.  2  is  given  on  a  separate  sketch  (Pig. 
5)  to  show  the  method  more  clearly. 

Fig.  5  illustrates  the  method  of  obtaining  the  point  D, 
on  which  the  centre  pin  is  fixed  for  the  trammel  to 
slide  on  while  working.  This  point  also  gives  the  length 
of  the  radius-rod.  This  sketch  is  reduced  one-half  in 
size  to  that  of  Fig.  2a,  but  the  letters  correspond  to  it. 
Having  set  out  the  axis  or  centre  line  of  the  column  (A 
B)  and  the  base  line  (AC)  (extending  the  latter  indefi- 
nitely) as  described  for  Fig.  la,  proceed  as  follows.  From 
A  as  a  centre,  and  from  A  to  B  as  a  radius,  describe  an 
arc,  as  indicated  by  the  dotted  line;  then  from  the  in- 
tersecting point  at  C  as  a  centre^  and  from  C  to  the 
point  at  B  as  a  radius  (as  indicated  by  the  dotted  line), 
describe  an  arc  until  it  cuts  the  base  line  at  K.  This 
done  add  the  distance  from  the  point  at  A  to  the  point 
at  K  to  the  base  line,  outward  from  the  point  at  C,  which 
gives  the  desired  point  D. 

The  trammel  should  be  set  out  on  a  wall  or  a  clean 
floor.  To  set  it  out,  first  draw  a  line  to  the  exact  height 
of  the  proposed  column,  as  A  B  on  Fig.  2a,  then  draw 
a  line  (indefinitely  in  length)  at  right  angles  to  A  B,  as 
shown  from  A  to  D.  This  line  A  B  is  the  axis  or  centre 
line  of  the  column,  and  the  line  A  D  is  the  base  line.  To 
construct  the  trammel,  take  two  rules,  each  the  length  of 
the  column,,  and  about  2  inches  wide,  and  1^/2  ii^-  thick ; 


METHODS  OF  WORK  181 


fix  one  on  each  side  of  the  axis  of  the  column,  taking  care 
to  keep  them  equidistant  and  parallel  to  the  axis,  and 
forming  a  grooved  space  about  2  inches  wide,  as  shown 
at  a,  a,  the  rules,  and  b  the  groove.  These  rules  are 
made  thicker  than  the  board  intended  for  the  floating 
rule,  so  as  to  allow  the  trammel  pencil  to  run  freely 
when  marking  the  diminished  line  on  the  board.  This 
is  shown  by  the  section  at  Fig.  1.  This  is  as  when  done 
in  a  temporary  way  on  a  floor,  but  a  better  way  is  to 
fix  the  rules  on  a  board  (a  flooring  board  will  be  found 
suitable).  This  makes  a  permanent  groove,  and  forms  an 
easy  ground  for  the  sliding  block  to  work  smoothly.  It 
also  allows  a  greater  space  for  a  thicker  board  for  the 
floating  rule. 

Fig.  2  shows  enlarged  details  of  the  groove  rules  (A, 
A,)  the  groove  (b,)  the  sliding  block  (B),  with  the  pin 
(H),  the  radius-rod  (F),  with  the  pencil  (G),  and  the 
board  for  the  floating  rule  (C),  with  the  diminished 
line.  Fig.  1  shows  a  section  of  Fig.  2.  The  letters  in 
all  figures  correspond  with  each  other.  Fig.  2a  shows 
the  whole  column  with  the  trammel  and  finished  floating 
rule  (C).  Make  the  radius-rod  about  2  inches  wide,  1 
inch  thick  and  in  length  a  little  longer  than  the  distance 
from  D  to  B,  and  the  half  diameter  of  base  of  the  shaft. 
The  sliding  block  (H)  is  about  4  inches  long  and  equal 
in  depth  and  width  to  that  of  the  sliding  groove  (b).  It 
should  be  made  smooth,  and  fit  the  groove  easily,  so  that 
it  will  slide  freely  from  end  to  end  when  working.  In 
the  exact  centre  of  the  block  fix  a  hardwood  pin  or  a 
round  nail  (H).  This  must  be  fixed  exactly  over  the 
axis  of  the  column,  and  so  fitted  that  it  will  run  imme- 
diately over  it  from  end  to  end.  Bore  a  hole  in  the  ra- 
dius-rod to  fit  this  pin,  then  from  the  centre  of  the  pin 
set  off  exactly  half  the  diameter  of  the  base  of  the  col- 


182  CEMENTS  AND  CONCRETES 


umn  on  the  radius-rod,  which  will  give  the  point  for 
the  pencil  hole  (G).  At  this  point  bore  a  hole  large 
enough  to  receive  a  pencil,  which  must  be  tightly  held  in 
it.  At  the  lower  end  of  the  radius-rod  cut  a  slot  just 
wide  enough  to  receive  the  center  pin  at  D. 

A  plan  of  the  radius-rod  with  the  slot  and  centre  pin 
is  ishown  at  Fig.  3  and  a  section  at  Fig.  4.  The  block 
beneath  the  radius-rod,  in  the  section  is  used  to  keep  the 
rod  level  with  the  rules  and  sliding  block,  as  shown  on 
Fig.  1.  To  ascertain  the  length  to  cut  the  slot,  place  the 
radius-rod  along  the  line  A  D,  and  the  pencil  at  the  out- 
side of  the  semi-diameter  at  the  base  of  the  column,  and 
slide  it  to  its  place;  mark  on  the  rod  where  the  centre 
pin  (D)  comes;  then  place  the  pencil  end  of  the  rod  at 
the  top  diameter,  and  mark  the  rod  again  at  the  centre 
pin;  this  will  give  the  length  of  the  pin.  Having  made 
the  trammel,  provide  a  stout  board  to  form  the  floating 
rule  (cc).  This  board  should  be  planed  on  both  sides 
and  one  edge.  Place  it  near  the  rules  a  a,  keeping  the 
planed  edge  outwards,  and  parallel  with  the  axis  or 
centre  line  of  the  column.  This  allows  the  planed  edge 
of  the  floating  rule  to  be  used  as  a  straight  edge  to 
plumb  by  when  fixing  the  top  and  bottom  rims  or  mould- 
ings, w^hich  are  used  as  guides  and  bearings  when  float- 
ing the  column.  Place  the  sliding  block  in  position,  and 
lay  the  radius-rod  over  the  center  pin,  and  the  pin  of  the 
sliding  block,  keeping  the  rod  in  a  line  with  D  A,  tak- 
ing care  that  the  pencil  is  in  its  true  position ;  then  care- 
fully move  it  upwards,  and  pressing  the  pencil  gently 
upon  the  board  which  will  give  the  line  for  cutting  the 
diminishing  floating  rule.  The  floating  edge  is  strength- 
ened by  nailing  a  strip  of  sheet  iron  on  the  board  in  a 
similar  w^ay  to  that  in  which  a  mould  plate  on  a  running 
mould  is  treated.    This  is  of  special  use  when  floating 


METHODS  OF  WORK 


m 


diminished  fluted  columns  or  pilasters,  as  the  thin  and 
sharp  edge  allows  the  flutes  to  be  more  easily  formed. 
The  diminished  line  on  the  metal  plate  can  also  be 
formed  with  the  trammel. 

A  column  trammel  can  also  be  used  for  setting  out 
other  diminished  floating  rules  for  columns  less  in  size 
than  the  original  one.  The  only  alteration  required  for 
this  purpose  is  to  alter  the  point  D  to  -suit  the  size  of  the 
proposed  column,  and  the  shortening  of  the  radius-rod. 
It  will  be  seen  that  the  floating  rules  for  both  columns 
are  made  long  enough  to  bear  on  the  base  and  necking 
mouldings,  but  it  is  usual  to  make  them  shorter  bo  as  to 
bear  on  cast  or  run  rims  or  collars,  which  are  fixed  at 
the  top  and  bottom  of  the  shaft. 

Constructing  Plain  Diminished  Columns. — Plain 
diminished  columns  and  pilasters  are  formed  with  a 
diminished  rule  fashioned  at  both  ends  to  work  on  the 
necking  and  base  mouldings  (termed  rims),  or  on  collars. 
The  method  of  making  rims  and  collars,  which  are  used 
as  bearings,  is  as  described  for  diminished  fluted 
columns. 

To  Set  out  the  Flutes  of  Diminished  Column, — The 
annexed  illustration  No.  10  elucidates  the  method  of  set- 
ting out  the  flutes  of  a  column.  Fig.  1  shows  the  half 
plan  of  a  column ;  A  is  the  plan  of  the  flutes  a'u  the  base, 
and  B  the  plan  at  the  top  of  the  shaft.  Fig.  2  shows  the 
elevation  of  the  column,  with  the  various  parts  marked. 
Fig.  3  shov\^s  the  plan  and  centres  for  setting  out  the 
flutings  for  the  different  orders  with  arrises  or  with  fil- 
lets. A  fluted  column  may  be  divided  into  twenty, 
twenty-four,  or  twenty-six  flutes,  according  to  the  style 
or  order.  There  are  two  different  sorts  of  flutes  used. 
One  is  worked  to  an  arris,  and  sunk  down  in  different 
depths,  one  of  which  is  described  by  the  fourth  part  of 


CEMENTS  AND  CONCRETES 


P  U  AIM 

—DiiMiNisHED  Fluted  Columns. 

NO.  10. 


METHODS  OF  WORK 


185 


the  circle,  one  by  the  sixth,  and  others  by  the  half 
circle,  as  shown  at  C,  D,  E,  Fig.  3. 

The  square  or  fillet  of  the  second  kind  is  equal  to  one- 
third  part  of  the  flute.  It  will  be  seen  in  Fig.  2  that 
two  lines  are  shown  at  the  top  of  the  flutes.  The  lower 
one  shows  how  the  flutes  finish,  when  the  fourth  and 
sixth  depths  are  taken,  and  the  top  line  when  the  half- 
circle  is  taken  together  with  the  fillets.  Flutes  that 
finish  with  an  arris  are  usually  employed  for  columns  in 
the  Doric  order,  and  those  that  finish  with  fillets  are  used 
in  the  other  orders.  The  fillets  or  lists  at  the  top  and 
bottom  of  the  shaft  of  a  column,  which  serve  to  divide 
the  shaft  from  the  capital  and  base  mouldings,  are  com- 
monly called  the  upper  and  lower  fillets,  and  sometimes 
the  horizontal  fillets,  but  in  architecture  they  are  known 
as  ^'cinctures."  The  curved  parts  at  the  top  and  bottom 
of  the  shaft  which  are  iisually  curved  into  the  upper  and 
lower  fillets  by  a  concave  curve  or  inverted  cavetto,  are 
in  architecture  termed  ' '  apophygis. ' ' 

Constructing  Diminished  Fluted  Columns. — The 
formation  of  diminished  fluted  columns  by  means  of  a 
running  mould  is  an  absorbing  and  vexed  topic  among 
plasterers,  and  many  ingenious  plans  have  been  advanced 
for  the  construction  of  hinged  and  spring  running 
moulds,  and  diminished  running  rules.  I  have  known 
more  than  one  self-improving  plasterer  who  has  ex- 
pended a  vast  deal  of  time  and  lime  (not  forgetting 
plaster)  to  prove  by  actual  practice  the  possibility  of 
running  a  diminished  fluted  column,  while  others  have 
been  content  to  work  them  by  theory,  forgetting  that  an 
ounce  of  practice  is  worth  a  ton  of  theory.  Some  men 
thought  they  had  accomplished  a  feat  when  they  had 
run  a  single  flute  with  a  hinged  mould,  between  two  run- 
ning  rules  fixed  to  form  diminution  in  width,  forget 


186  CEMENTS  AND  CONCRETES 


ting  or  not  knowing  that  flutes  diminish  in  depth  as  well 
as  width. 

The  difference  in  depth  of  flutes,  at  the  base  and  the 
top  of  the  shaft,  is  shown  at  A,  the  base,  and  B,  the  top, 
in  Fig.  1,  illustration  No.  10.  Running  moulds  have  also 
been  made  with  springs  to  regulate  the  diminish  in 
depth,  but  their  action  was  uncertain,  and  they  are  also 
too  expensive  for  the  purpose.  Another  form  of  run- 
ning mould  was  made  by  fixing  wire,  catgut,  or  leather 
on  one  end  of  one  of  the  slippers,  and  on  the  upper  edge 
of  the  stock,  so  that  the  slipper,  when  being  forced  up 
the  diminished  space  between  the  running  rules,  became 
more  angular,  or  in  other  words,  the  slipper  on  which 
one  end  of  the  wire  was  attached  was  higher  up  the 
diminished  space  than  the  other  slipper,  and  thus  caused 
the  stock  to  cant  forward,  or  be  drawn  out  of  an  up- 
right, and  reduce  the  depth  of  the  flute.  The  stock  in 
this  case  is  connected  to  the  slippers  not  by  hinges,  but 
by  a  pivot  inserted  at  each  slipper  to  allow  the  stock 
to  cant  forward  when  pulled  by  the  wire.  This  form 
of  mould  also  proved  to  be  too  erratic  in  its  working 
to  be  of  useful  service.  Running  moulds  having  the 
stock  connected  to  a  slipper  at  each  side  by  means  of 
two  hinges  (termed  a  double-hinged  mould)  allow  the 
mould  to  assume  an  angular  or  slanting  form  as  it  passes 
up  the  diminished  space,  thus  forming  a  diminution  in 
the  width  of  flute,  but  it  does  not  form  it  with  a  true 
arc  all  the  way.  On  the  contrary,  it  assumes  an  elliptical 
form  which  becomes  more  and  more  pronounced  as  it 
reaches  the  top  of  the  shaft. 

The  nearest  approach  to  perfection  in  running  dimin- 
ished flute  is  performed  by  means  of  a  running  mould 
made  with  hinged  slippers  as  described,  but  having  the 
mould  plate  and  stock  cut  through  the  centre  of  the 


METHODS  OF  WORK 


187 


profile,  the  two  parts  being  then  connected  by  a  hinge. 
This  form  of  running  mould  (termed  a  ^'triple-hinged 
mould '0  allows  the  mould  to  collapse  in  the  form  of  a 
V  on  plan,  and  the  slippers  to  run  level  or  parallel  with 
each  other,  thus  forming  each  half  of  the  flute  alike,  and 
at  right  angles  from  the  centre.  Still  this  has  the  defect 
of  forming  the  flute  without  the  necessary  decrease  in 
depth. 

A  method  for  diminishing  the  depth  of  the  flutes  is  to 
make  the  running  rules  with  a  diminish  on  face,  or 
rather  to  make  them  with  an  increasing  thickness  towards 
the  top  ends,  so  that  the  mould  when  running  up  on  the 
increasing  thickness  will  form  a  corresponding  de- 
creased depth  of  flute.  When  running  a  fluted  column 
by  this  process,  the  running  rules  are  fixed  flush  with 
the  face  line  of  the  fillets.  Only  one  flute  can  be  run  at 
a  time,  but  twelve  may  be  in  band  at  the  same  time.  As 
there  are  generally  twenty-four  flutes  in  a  column, 
twelve  rules  would  be  required  to  keep  a  couple  of 
plasterers  going.  When  the  fi,^st  set  of  flutes  are  run, 
the  rules  are  taken  off  and  fixed  to  run  the  remaining 
flutes.  When  all  are  run,  the  returned  ends  at  top  and 
bottom  require  to  be  made  good.  It  will  be  seen  that  the 
running  rules  for  this  method  must  be  carefully  made 
and  fixed  to  ensure  true  lines  and  forms.  It  will  be 
understood  that  a  bed  or  ground  must  first  be  formed 
as  a  guide  for  setting  out  and  fixing  the  running  rules 
on.  This  is  done  with  the  aid  of  a  diminished  floating 
rule.  It  will  also  be  self-evident  ^hat  the  floating  rule 
would  be  more  profitably  employed  for  forming  the 
entire  shaft  with  the  flutes,  thus  dispensing  with  run- 
ning rules  and  hinged  moulds.  This  method  of  running 
the  flutes  is  slo^^'  and  tedious^  but  tne  worst  part  is  that 
the  flutes  are  not  true  segments ;  in  fact,  the  whole  of  the 


188  CEMENTS  AND  CONCRETES 


methods  mentioned  are  more  or  less  a  rule  of  thumb,  un- 
certain and  inaccurate. 

A  knowledge  of  the  rudiments  of  geometry  will  prove 
that  the  true  form  of  a  diminished  and  swelled  fluted 
column  cannot  be  run  with  a  mould,  however  ingeniously 
made.  This  may  be  proved  by  cutting  a  plaster  or  card- 
board disc  to  the  former  radius  of  a  single  flute,  and  de- 
scribing a  line  round  it  on  a  board.  This  would  be  the 
form  the  mould,  when  at  right  angles  at  the  bottom  of 
the  shaft,  would  give  the  flute.  Then  place  the  disc  in 
an  oblique  position  (the  same  as  the  hinged  mould  would 
be  at  the  top),  and  project  the  plans  by  means  of  a  set 
square  on  to  the  board.  It  will  be  seen  that  the  mould 
would  give  the  flute  an  elliptical  form.  It  may  be 
further  explained  by  stating  that  when  the  mould  is 
square  at  the  base,  or  at  right  angles  with  the  vertical 
running  rules,  the  form  of  the  flute  would  be  a  true 
segment;  but  when  the  mould  is  moved  up  the  dimin- 
ished space  between  the  rules,  it  assumes  an  oblique  or 
slanting  position.  It  gives  the  flute  an  elliptical  form, 
which  increases  and  becomes  more  pronounced  as  it  ap- 
proaches the  necking.  It  may  be  said  that  the  pointed 
or  elliptical  defects  can  be  filled  in  and  worked  fair 
with  circular  hand  floats,  but  this  plan  necessitates  a 
series  of  hand  floats  to  fit  the  ever-varying  widths  and 
depths  of  the  flutes. 

It  may  seem  unnecessary  to  describe  the  above  meth- 
ods, and  then  to  point  out  their  defects.  However,  the 
methods  and  defects  are  given  to  prevent  the  rising  plas- 
terer falling  into  the  same  errors,  and  to  enable  him  to 
resist  and  rebut  the  arguments  that  are  so  often  ad- 
vanced by  some  men,  who  persistently  assert  that  their 
own  particular  way  (genera-lly  one  of  the  methods  al- 


METHODS  OF  WORK  189 

ready  mentioned)  is  the  correct  and  only  way  of  proper- 
ly performing  this  different  bnt  interesting  operation. 

It  is  worthy  of  note,  to  show  the  interest  taken  in 
this  subject  that  a  patent  was  obtained  for  a  running 
mould  and  process  for  forming  diminished  fluted  col- 
umns, in  1878,  which  obtained  a  provisional  protection 
for  ^'improvements  in  moulds  or  templates  for  running 
stucco  or  ceinent  tapered  fluted  columns.''  The  follow- 
ing is  a  copy  of  the  specification  in  extenso: — 

This  invention  relates  to  the  running  of  stucco  or  ce- 
ment in  forming  fluted  or  other  columns,  pillars,  or  pi- 
lasters, and  similar  surfaces^  in  a  more  simple,  economi- 
cal, and  expeditious  manner  than  heretofore;  and  the 
nature  and  novelty  of  the  invention  as  applied  for  run- 
ning or  making  the  body  part  of  a  fluted  tapered  col- 
umn of  stucco  or  cement,  consisting  in  constructing  a 
short  box-shaped  template,  having  two  sides  joined  to- 
gether by  a  back  plate  outside,  with  a  handle  upon  it, 
for  drawing  it  up  and  down  the  column,  and  with  an 
open  space  inside  the  back  between  the  sides  open  above 
and  below,  equal  to  any  desired  section  or  segment  of 
the  column  at  its  base  or  widest  part,  into  which  the 
column  is  equally  divided  by  narrow  longitudinal 
strips  of  wood,  against  which  the  inner  edge  and  end 
surfaces  of  the  sides  of  the  template  slide  close,  so  as  to 
prevent  the  escape  of  the  semi-liquid  or  stucco.  A  thin 
elastic  segmental  mould  plate  is  hinged  or  jointed  at  its 
ends  to  the  inner  faces  or  edges  of  the  template,  formed 
in  its  inner  scraping  edge  to  correspond  to  the  segmental 
curve  of  the  base  of  the  column,  with  rounded  pro- 
jections corresponding  to  the  flutes  to  be  formed  on  the 
column.  This  plate  and  its  hinges  are  laid  at  an  angle 
highest  at  the  inner  scraping  edge,  and  inclined  down- 
wards towards  the  back,  leaving  a  space  between  it  and 


190  CEMENTS  AND  CONCRETES 


the  back  for  the  free  passage  or  escape  of  the  super- 
fluous stucco  or  cement  scraped  off  the  column  during 
the  ascent  of  the  mould  along  the  column  on  its  longi- 
tudinal shaping  strips  before  mentioned. 

^  ^  The  one  end  or  side  of  the  mould  is  made  to  slide  or 
contract  laterally  in  slots  or  other  equivalent  guides  in 
the  back  of  the  mould  frame  as  it  ascends  along  the  con- 
tracting or  tapering  longitudinal  laths,  the  thin  plate 
bending  or  yielding  down  in  a  curvilinear  form  on  its 
end  hinges  before  mentioned,  so  as  to  bulge  inwards  while 
bending  downwards^  and  so  contract  the  column  in  a 
nearly  true  radical  and  segmental  form  from  the  bottom 
to  the  top  of  the  column,  the  angle  at  which  the  scrap- 
ing mould  plate  is  set  on  its  hinges  determining  this  con- 
traction of  the  scraping  centre  edge  of  its  segment  radi- 
cally in  a  ratio  corresponding  to  the  contraction  of  the 
lengths  of  the  segment  and  moving  sides  of  the  mould, 
which,  for  large  moulds  and  columns,  might  be  car- 
ried and  drawn  up  by  handles  secured  to  the  tops  of 
the  ends  of  the  moulds  with  ropes  led  up  and  over  pul- 
leys at  the  top  of  the  column,  thence  down  to  the  hand 
of  the  operators,  so  that  the  mould  may  be  raised  and 
lowered  at  pleasure  to  form  the  whole  segment  of  the 
column  from  the  bottom  to  the  top  in  nearly  as  simple 
and  efficient  a  manner  as  plain  mouldings  are  at  present 
run  by  the  usual  simple  edge  scraping  moulds,  one  seg- 
.  ment  being  run  after  the  other  in  succession  until  the 
column  is  finished. 

' '  For  plain  or  other  forms  of  columns  the  inner  scrap- 
ing edge  of  the  mould  plate  is  made  to  correspond  to  the 
tapered  surface  of  the  column  to  be  formed  plain,  seg- 
mental, or  fluted  as  desired ;  and  for  flat,  square,  or  polyg- 
onal columns,  which  do  not  require  a  segmental  mould 
scraper,  this  would  be  made  straight,  either  plaia  or 


METHODS  OF  WORK 


191 


iluted,  as  desired  on  its  scraping  edge,  and  set  horizontal- 
ly on  its  hinges,  instead  of  at  an  angle  as  described  for 
the  segmental  mould  scraper  for  forming  round  col- 
umns ;  and  this  mould  scraping  plate  in  any  case  is  pre- 
ferred to  be  made  of  thin  elastic  steel  or  tempered  cop- 
per or  brass,  which  would  bend  and  contract  the  flutes  or 
ridges  on  the  surface  of  the  columns  or  pillars,  equally 
and  proportionally  to  the  several  parts  of  the  column 
over  which  the  mould  is  traversed.  Although  the  mould 
or  template  has  been  described  as  made  with  only  one 
of  its  ends  movable  laterally,  it  is  to  be  understood  that 
both  ends  or  sides  may  be  fitted  so  as  to  move  in  a 
similar  manner  to  suit  different  kinds  of  work. 

This  patent  method  would  be  better  understood  if  it 
had  been  illustrated.  No  provision  for  diminishing  the 
depth  of  the  flutes  is  given  in  this  method.  The  use  of 
flexible  metal  for  diminishing  purposes  cannot  be  relied 
on  for  accurate  work. 

Another  method  for  forming  diminished  fluted  col- 
umns is  thus  performed : — Make  a  single  flute  in  plaster, 
and  use  it  as  a  mould  for  casting  reverse  flutes  composed 
of  fibrous  plaster.  After  casting  as  many  reverse  flutes 
as  there  are  flutes  in  the  proposed  column,  indurate  them 
with  litharge  oil  or  paraffin  wax.  Casts  of  the  necking 
and  base,  each  with  about  3  inches  of  the  fluted  shaft,  are 
fixed  on  the  brick  core.  The  shaft  is  then  laid  with 
Portland  cement  (or  other  desired  cement)  and  sand  un- 
til within  about  one-third  of  the  line  of  fillets,  and 
while  this  stuff  is  still  soft,  take  a  reverse  flute 
(previously  oiled)  and  press  it  into  position,  using  the 
cement  flutes  at  the  necking  and  base  as  guides  for  fix- 
ing, and  using  a  diminished  floating  rule  to  prove  the 
outline.  Repeat  this  process  until  all  the  flutes  in  the 
column  are  filled  with  reverse  flutes.    The  intervening 


192  CEMENTS  AND  CONCRETES 


spaces  or  fillets  are  then  filled  in  with  gauged  cement 
until  flush  with  the  outer  surface  of  the  reverse  flutes, 
and  further  regulated  with  the  floating  rule.  When  the 
stuff  is  set,  the  reverse  flutes  are  extracted,  and  any  de- 
fects in  the  flutes  made  good.  On  the  care  in  fixing  the 
reverse  flutes  and  filling  in  the  fillets  depends  the  success 
of  this  method. 

Diminished  fluted  columns  are  also  made  by  casting 
two  vertical  halves,  and  then  fixing  them  on  the  brick 
core.  The  halves  are  fixed  by  means  of  cement  dots, 
which  are  laid  on  the  core  at  intervals.  (Corresponding 
dots  are  laid  on  the  interior  of  the  casts.  The  casts 
are  then  pressed  on  the  core  until  the  dots  meet,  and 
both  halves  are  in  proper  position.  The  cast  work  is 
made  solid  with  the  core  by  pouring  a  thin  and  weak 
solution  of  cement  and  sand  into  an  orifice  at  the  neck- 
ing. 

The  cement  and  sand  should  be  mixed  in  the  propor- 
tion of  one  of  the  former  to  five  of  the  latter.  This 
gauge  has  sufficient  binding  power  and  strength  for  this 
purpose,  and  is  not  liable  to  expand  or  contract  in  wet  or 
dry  weather.  This  process  is  useful  for  small  work,  and 
makes  a  good  job  when  cleanly  cast  and  neatly  fixed.  The 
necking  with  the  capital  and  the  base  may  be  fixed  be- 
fore or  after  the  shaft  casts  are  fixed,  according  to  cir- 
cumstances. The  shaft  casts  are  best  formed  in  a  reverse 
casting  mould. 

Another  method  of  casting  a  diminished  fluted  col- 
umn is  effected  by  making  a  reverse  casting  mould.  Fix 
it  round  the  core,  and  pour  the  gauged  material  in  at 
the  top  of  the  necking  mould.  By  using  a  reverse 
casting  mould  made  with  a  plaster  face  and  a  wood  back- 
ing, or  a  mould  made  in  fibrous  plaster,  the  whole 
column  with  the  core  can  be  made  in  one  piece.  Hoi- 


METHODS  OF  WORK 


193 


low  columns,  compoised  of  Portland  .cement  concrete, 
can  be  made  to  carry  any  weight  supported  by  a  stone 
column,  or  one  constructed  with  a  brick  core  of  equal 
diameter.  Cast  hollow  columns  are  made  by  temporarily 
fixing  a  wood  or  fibrous  plaster  core  tapered  to  one  end 
to  allow  it  to  be  withdrawn  when  the  concrete  is  set.  A 
rough  wooden  or  a  fibrous  plaster  hollow  core  is  used 
when  casting  a  hollow  column  in  situ.  The  core  in  this 
case  is  left  in. 

After  many  years'  experience  and  observation  on  this 
subject,  I  am  of  opinion  that  the  true  form  of  a  dimin- 
ished fluted  column  (composed  in  Portland  or  similar 
cement,  and  constructed  in  situ)  is  best  obtained  by 
hand,  with  the  aid  of  cement  rims  or  plaster  collars 
and  a  diminished  floating  rule.  Most  plasterers  will 
admit  that  what  can  be  and  is  done  in  stone  or  wood, 
can  be  done  equally  well  in  cement  or  planter.  A  plaster- 
er has  one  advantage,  inasmuch  as  he  can  add  as  well 
as  subtract  when  forming  circular  surfaces,  whereas  the 
mason  can  only  subtract.  The  two  methods  hereafter 
given  for  forming  diminished  fluted  columns  by  hand 
are  simple,  speedy,  and  accurate.  They  are  on  one  prin- 
cipal, and  each  may  be  used  as  circumstances  require: 
one  is  termed  the  ^^rim  method,"  and  the  other  the 
' '  collar  method. ' ' 

Forming  Diminished  Fluted  Column  ty  the  Bim 
Method. — First  make  models  of  the  half  circumferences 
of  the  astragal  or  necking  and  base  mouldings,  each 
having  about  4  inches  of  the  fluted  shaft,  as  shown  at 
Fig.  1,  the  plan  and  Fig.  2,  the  elevation,  on  illustra- 
tion No.  10.  To  make  the  models,  cut  a  mould  plate  to 
fit  each  of  the  full-sized  mouldings,  and  the  required 
size  of  the  shaft,  and  horse''  them  with  radius-rods, 
and  run  a  little  over  one-half  of  each  circumference  in 


194  CEMENTS  AND  CONCRETES 


plaster,  and  then  cut  them  to  the  exact  half  circumfer- 
ence. This  done,  set  out  the  flutes,  then  cut  them  out 
and  form  the  returned  ends.  The  method  of  setting  out 
the  flutes  on  the  ends  of  the  models  is  shown  on  the  plan 
at  Fig.  1.  A  is  the  plan  at  the  base,  and  B  the  plan  at 
the  top  of  the  shaft.  The  returned  ends  of  flutes  are 
shown  on  the  elevation,  Fig.  2.  Add  the  square  plinth 
to  the  base,  as  shown  on  the  plan  at  Fig.  1,  which  com- 
pletes the  models.  Piece  mould  the  models  in  plaster, 
and  then  cast  as  many  half  astragal  and  bases  as  re- 
quired. The  materials  used  for  the  casts  must  be  of  the 
same  kind  as  intended  for  the  shaft.  The  brick  or  core 
of  the  column  is  now  cleaned  and  well  wetted,  and  then 
the  astragal  and  bases  are  fixed  in  position,  using  the 
diminished  floating  rule  to  prove  if  they  are  central,  and 
the  fillets  linable  with  each  other.  Apply  a  plumb  rule 
on  the  back  edge  of  the  floating  rule  to  test  if  the  astragal 
and  base  are  concentrical  and  parallel  with  each  other. 
When  these  half  casts  are  fixed  together  on  the  shaft  they 
are  termed  ^'rims. "  The  intermediate  space  on  the 
shaft  is  then  filled  in  and  ruled  off  with  the  diminished 
floating  rule,  using  the  rims  as  bearings  and  guides  for 
forming  the  fillet  line  of  shaft. 

The  methods  of  forming  a  diminished  fluted  column 
by  the  ^^rim  method''  is  further  elucidated  by  the  an- 
nexed illustration.  No.  11.  This  shows  an  elevation  of 
the  brick  core  of  a  shaft  with  the  astragal  rim,  A  and 
the  base  rim,  B,  fixed  in  position.  D  is  the  diminished 
floating  rule  in  position  for  floating  the  main  or  fillet  line 
of  the  shaft.  The  method  of  using  a  diminished  flute 
rule  for  the  flutes  is  illustrated  in  the  ' '  collar  method. ' ' 

A  second  diminished  floating  rule  is  required  to  form 
the  back  surface  of  the  flutes.  This  can  be  quickly  made 
by  laying  the  first  rule  flat  on  the  floor,  and  from  this^ 


METHODS  OF  WORK  195 


with  compasses,  describe  the  back  line  of  the  flute  on 
another  board,  which  is  afterwards  cut  to  the  desired 


-Floated  Fluted  Columns,  Kim  Method. 
NO.  n. 


line.  This  rule  is  used  as  a.  long  joint  rule  to  form  the 
flutes.  The  rule  should  be  worked  with  uniform  pres- 
sure, the  man  at  the  top  working  in  unison  with  the  man 


196  CEMENTS  AND  CONCRETESi 


at  the  bottom,  both  working  the  rule  with  a  circular 
cutting  motion.  The  flutes  are  fined  down  by  the  aid  of 
a  small  float  semicircular  in  section.  For  extra  large 
columns  three  floats  should  be  used — No.  1  cut  to  the 
top  section,  No.  2  cut  to  the  middle  section,  and  No.  3 
cut  to  the  bottom  section.  The  length  of  the  floats  may 
vary  from  5  inches  to  7  inches,  according  to  the  height  of 
the  column.  If  the  columns  are  required  with  a  smooth 
surface,  the  flutes  are  worked  as  above,  but  the  floats  are 
covered  with  fine  felt,  leather,  or  rubber,  and  the  sur- 
face finished  smooth  with  short  joint  rules  or  with  pieces 
of  flexible  busks.  The  cast  parts  of  the  shaft,  to  the 
fillet  members  of  the  astragal  and  the  base,  should  be 
keyed  with  a  drag,  so  that  the  whole  shaft,  from  arris  to 
arris  of  the  astragal  and  base  fillets^  can  be  fined,  thus 
giving  a  uniform  texture  and  color,  and  avoiding  a  sur- 
face joint  of  the  cast  work  and  the  fined  work. 

A  modification  of  this  method  is  as  follows: — The 
lower  horizontal  jfiUet  of  the  shaft  and  the  base  mouldings 
are  caist  separately,  the  fillet  part  being  used  as  bear- 
ings for  floating  the  shaft,  as  already  described,  and  the 
base  is  fixed  after  the  shaft  is  fined.  This  plan  is  useful 
for  some  purposes,  such  as  for  extra  large  columns,  as  it 
gives  more  freedom  for  working  the  shafts  and  the  bases 
are  not  so  liable  to  get  injured  while  working  over  them. 

Running  Diminished  Fluted  Column  iy  the  Collar 
Method, — Run  a  plaster  collar  about  IV2  inches  wide  to 
the  diameter  of  the  top  horizontal  fillet  of  the  shaft. 
The  thickness  must  be  regulated  according  to  the  space 
between  the  brick  core  and  the  line  of  fillet.  Cut  this 
collar  in  halves  and  fix  them  on  the  brick  core,  keeping 
the  under  side  in  a  line  and  level  with  the  top  of  the 
proposed  fillet  of  the  shaft.  Run  another  collar  to  fit 
the  horizontal  fillet  at  the  base  of  the  3haft,  and  fix  the 


METHODS  OF  WORK 


197 


upper  side  of  this  one  level  w^ith  the  bottom  edge  of  the 
fillet  at  base  of  the  shaft.  This  done,  make  two  plaster 
models  of  the  flutes,  one  for  the  top  and  one  for  the 
bottom  of  the  shaft,  each  about  3  inches  wide,  and  in 
thickness  according  to  the  brick  core,  the  diameter  being 
taken  about  1  inch  above  the  returned  ends  of  the  flutes 
at  the  top  and  bottom  of  the  shaft.  These  models  are 
set  out  and  made  as  described  for  the  first  method,  but 
using  plaster  instead  of  cement  for  the  casts.  The  plaster 
casts  are  fixed  in  position,  and  then  the  brick  core  is 
laid  and  ruled  off,  using  the  main  diminished  floating 
rule  (and  the  plain  collars  as  bearings)  for  forming  the 
main  contour  or  line  of  the  vertical  fillets,  including  the 
horizontal  or  top  and  bottom  fillets  of  the  shaft,  and 
using  the  diminished  flute  floating  rule  (and  the  plaster 
models  of  the  flutes  as  bearings)  for  forming  the  flut3s. 
This  done,  the  fluted  collars  are  cut  out,  the  spaces  filled 
in  and  ruled  off,  and  the  returned  ends  of  the  flutes 
are  formed,  and  then  the  whole  shaft  is  fined  while  the 
work  is  green.  The  fillet  collars  are  then  cut  out,  and 
the  astragal  and  base  mouldings  are  then  fixed,  thus 
completing  the  column.  It  will  be  seen  that  this  method 
entirely  dispenses  with  joints  between  cast  and  floated 
work  on  the  shaft,  and  allows  it  to  be  fined  in  one  opera- 
tion. 

The  method  of  running  diminished  fluted  columns 
with  the  aid  of  collars  is  further  elucidated  by  the  an- 
nexed illustration  No.  12.  A  C  is  the  top  fillet  collar,  B  C 
the  bottom  fillet  collar,  and  F  C  and  F  C  are  the  top  and 
bottom  flute  collars  fixed  on  the  brick  core  of  the  column. 
D  R  is  the  main  diminished  floating  rule  in  position  for 
forming  the  main  contour  or  fillet  line  of  the  column. 
This  rule  is  rebated  at  the  top  to  allow  for  a  bearing  on 
the  top  as  well  as  on  the  edge  of  the  collar.    This  rule 


198  CEMENTS  AND  CONCRETES 


also  forms  the  profile  of  the  top  and  bottom  horizontal 
fillets,  and  the  curved  parts  of  the  shafts  below  the  top 
fillet  and  above  the  bottom  fillet.     F  R  is  the  flute 


Forming  Fluted  Columns — Collar  MeIhod. 


NO.  12. 


floating  rule  in  position  when  forming  the  flutes.  The 
ends  of  this  rule  as  shown  bear  on  the  back  surface  of 
a  flute  as  indicated  by  the  dotted  lines.  A  portion  of  the 
astragal  moulding,  A,  with  a  part  of  the  shaft  is  shown 


METHODS  OF  WORK 


199 


so  as  to  indicate  the  position  to  fix  the  fillet  collar^  A  C ; 
a  portion  of  the  base  moulding;,  B  with  a  part  of  the 
shaft,  is  also  given  to  show  the  position  of  the  bottom 
fillet  collar,  B.  C.  It  will  be  seen  that  these  collars  form 
fair  bed  for  the  astragal  and  base  mouldings,  and  when 
taken  off  they  leave  true  joints  as  indicated  by  the  ar- 
rows at  A  and  B. 

A  modification  of  the  above  methods  for  forming  the 
fillets  and  flutes  is  effected  as  follows: — Fill  in  the  spaces 
on  the  shaft  between  the  collars  in  this  method — or  the 
rims  in  the  former  method — and  rule  them  off  with  a 
main  diminished  floating  rule  as  already  described  and 
when  the  stuff  is  firm  but  not  set,  the  positions  and  forms 
of  the  fillets  and  flutes  are  set  out  on  the  floated  surface, 
then  the  flutes  are  cut  out  by  hand  by  means  of  gouges 
and  drags,  and  afterwards  fined  as  already  described. 
This  system  is  specially  useful  for  small  columns. 

For  extra  high  columns  it  will  be  found  difficult  to 
work  a  floating  rule  to  form  the  whole  height  of  the 
column  in  one  operation,  in  fact,  for  some  columns  to  be 
seen  in  cities,  which  are  20  feet  to  30  feet  high,  and 
even  higher,  it  would  be  impossible  to  form  them  with 
one  floating  rule.  It  is  therefore  noiEessary  to  divide  the 
column  into  two  or  more  sections^  and  cut  the  floating 
rules  accordingly.  In  this  case  two  or  more  plaster  col- 
lars about  3  inches  wide,  and  made  to  the  exact  circum- 
ference of  the  column  at  the  point  of  division,  are  re- 
quired. These  collars  are  then  temporarily  fixed  in  posi- 
tion to  act  as  screeds,  and  after  the  whole  surface  of  the 
column  is  filled  in  and  ruled  off,  the  collars  are  cut  out 
and  the  spaces  filled  in,  and  then  the  whole  surface 
fined  in  one  operation.  Three  or  even  more  floats,  as 
already  described,  are  required  for  the  fining  of  high  or 
massive  columns. 


200  CEMENTS  AND  CONCEETES 


Having  now  briefly  reviewed  the  more  or  less  useful 
methods,  and  described  some  of  the  most  useful  and 
practical  methods,  the  conclusion  to  be  drawn  is,  that 
diminished  fluted  columns  are  best  done  by  working 
them  b}^  hand,  with  the  aid  of  diminished  floating  rules 
and  cast  or  run  bearings.  This  first  or  rim  method  will 
be  found  useful  for  many  purposes;  but  the  collar'meth- 
od,  with  the  addition  of  intermediate  collars  for  extra 
high  columns,  is  the  best  for  general  use. 

Diminished  Fluted  Pilasters. — Pilasters  are  said  to  be 
a  Roman  invention.  They  bear  an  analogy  to  columns 
in  their  parts,  have  the  same  names  and  standard  of 
measurements,  and  are  diminished  and  fluted  on  the  same 
principals.  When  pilasters  are  placed  behind  columns, 
and  very  near  them,  they  should,  not  project  above  one- 
eighth  of  their  diameter;  but  if  they  are  from  6  to  10 
feet  behind  the  column,  as  in  large  porticoes  and  per- 
istyles, they  should  project  at  least  one-sixth  of  their 
diameter.  When  they  are  in  a  line  with  columns,  their 
projection  should  be  regulated  by  that  of  the  columns. 
When  pilasters  are  used  alone  as  principals  in  composi- 
tion, they  should  be  made  to  project  one-fourth  of  their 
diameter  to  give  regularity  to  the  returned  parts  of  the 
capitals.  The  process  for  forming  pilasters  is  the  same 
as  for  columns. 

Panelled  Coves. — Large  coves,  segmental  or  elliptical 
on  section,  having  their  surfaces  panelled  with  mouldings 
which  spring  from  the  back  or  above  a  wall  or  main 
cornice,  and  finish  at  or  intersect  with  a  beam  or  other 
moulding  at  the  top  or  crown  of  the  cove,  require  to  be 
carefully  set  out  and  screeded.  The  floating  is  done 
from  two  horizontal  screed*  made  at  the  top  and  bottom 
of  the  cove,  and  from  these  vertical  screeds  are  formed, 
and  then  the  intermediate  spaces  or  bays  are  filled  in 


METHODS  OF  WORK 


201 


and  ruled  off  with  a  floating  rule  bearing  on  the  vertical 
screeds.  The  horizontal  screeds  are  easily  made,  but  the 
vertical  ones  require  special  care  to  insure  all  being  uni- 
form in  section.  These  screeds  are  formed  with  a  tem- 
plate cut  to  the  desired  section,  and  about  2  inches  thick. 
For  large  coves  they  are  made  with  three  or  more  pieces 
of  wood.  The  most  correct  and  expeditious  way  of 
forming  circular  screeds  is  by  the  ''pressed  screed" 
process. 


Section  of  Cove  Showing  Pressed  Screed  Process. 
NO.  13. 

Pressed  screeds  are  simple  and  expeditious  in  con- 
struction. They  form  accurate  grounds  for  floating  pur- 
poses and  for  running  mouldings  on  circular  surfaces. 
The  method  of  forming  pressed  screeds  and  floating  co^^es 
is  shown  in  the  accompanying  illustration  No.  13.  This 
shows  the  section  of  a  cove  with  the  main  or  wall  cornice 
and  the  crown  moulding.     F  is  a  nib  rule  used  when 


202  CEMENTS  AND  CONCRETES 


running  the  main  cornice.  To  float  this  cove  for  the  run- 
ning of  vertical  mouldings,  first  form  the  top  and  bottom 
horizontal  screeds  (A  and  B)^  then  form  the  pressed 
screed.  This  is  effected  by  temporarily  fixing  the  . 
template,  G,  or  by  one  man  holding  it  on  the  bottom 
screed,  and  another  man  holding  it  on  the  top  screed, 
while  a  third  spreads  and  presses  the  gauged  coarse  stuff 
until  the  space  between  the  first  coating  and  edge  of  the 
template  is  filled  up,  then  drawing  the  trowel  down  each 
side  of  the  template  clears  off  any  superfluous  stuff. 


-Fig.  I,  Floating  Coves.   Yic.  2,  Levelling  Rule. 
NO.  14. 


The  template,  which  has  been  previously  oiled,  is  then 
removed,  leaving  a  narrow,  but  true  and  smooth  screed 
ready  for  working  on.  This  method  gives  a  truer 
screed,  especially  in  elliptical  or  long  circular  screeds, 
-  than  floating  or  working  with  a  template,  because  if  the 
template  is  not  worked  perfectly  vei1;ical,  the  curve  of 
the  screed  is  altered  and  not  true. 

The  subjoined  illustration  (No.  14)  elucidates  the 
method  of  forming  the  screeds  for  floating  cove  surfaces, 
also  for  floating  segmental,  elliptical,  or  any  other  form 


METHODS  OF  WORK 


203 


of  interior  and  exterior  angles  in  coves.  Fig.  1  shows  a 
plan  of  the  cove.  The  letters  in  this  sketch  correspond 
with  those  on  the  same  parts  in  the  section  on  illustration 
No.  13.  The  first  coating  and  the  various  bays,  after 
the  screeds  are  made^  are  indicated  by  crossed  diagonal 
lines  at  the  D's.  The  top  screed,  A,  should  be  levelled 
from  end  to  end  and  made  parallel  in  depth  with  the 
crown  moulding.  Their  levelness  is  tested  with  the  aid 
of  a  ^ levelling''  rule.  The  bottom  screed,  B,  should 
be  made  parallel  with  the  main  cornice,  so  that  the  pro- 
jection of  the  vertical  mouldings  will  be  uniform.  The 
vertical  screeds,  C,  are  next  formed,  making  the  first  two 
near  the  internal  angles,  then  two  at  the  external  angles. 
The  intervening  space  is  now^  set  out,  so  that  the  screeds 
may  be  8  to  10  feet  apart.  The  screeds  may  be  formed 
farther  apart  according  to  requirements.  If  there  are 
vertical  mouldings  to  be  run  in  the  cove,  the  screeds 
should  be  made  at  the  sides  of  the  proposed  mouldings. 
It  is  always  best  to  have  two  or  three  screeds  near  the 
angles,  so  as  to  give  a  bearing  for  the  floating  rule,  R. 
This  shows  the  position  of  the  rule  w^hen  floating  the  in- 
ternal angle.  The  external  angles  on  the  other  side  are 
formed  in  the  same  way.  The  distance  between  the 
screeds  used  for  floating  the  angles  can  be  regulated  ac- 
cording to  the  depth  or  form  of  the  angle.  It  will  be 
understood  that  the  floating  rule  must  be  sufficiently 
long  to  bear  on  two  vertical  screeds,  and  reach  to  the 
extreme  point  of  the  angle.  The  floating  rule,  R,  here 
shown  is  termed  a  grooved  floating  rule.  This  is  grooved 
on  both  sides,  as  shown  by  the  section,  S. 

Fig.  2  shows  the  elevation  of  a  levelling  rule  as  used 
for  levelling  dots  for  ceiling,  beam,  or  crown  screeds. 
This  is  similar  to  an  ordinary  parallel  rule,  but  with  the 
addition  of  a  fillet,  F,  nailed  flush  with  the  bottom  edge 


204  CEMENTS  AND  CONCRETES 


to  form  a  ledge  to  carry  the  spirit  level,  L.  The  level- 
ling rule  is  applied  on  the  dots  to  test  if  they  are  level ; 
this  is  proved  by  inspecting  the  spirit-level ;  if  one  dot  is 
too  full  it  must  be  depressed  until  the  levelling  rule  is 
level. 

Diminished  Mouldings. — Mouldings  that  diminish  in 
depth  or  projection  as  well  as  in  width  (termed  double 
diminished  mouldings'')  are  not  so  common  as  those  that 
diminish  in  width  only.  The  diminish  in  width  is  simple, 
and  is  obtained  by  the  aid  of  a  ''triple-slippered"  run- 
ning mould  and  two  running  rules  fixed  to  form  a 
diminished  space,  as  described  h-ereafter.  The  formation 
of  a  regular  and  pleasing  diminish  in  depth  greatly  de- 
pends on  the  profile  of  the  moulding.  A  moulding  hav- 
ing small  members,  especially  at  the  sides,  is  more  diffi- 
cult to  diminish  than  one  having  large  members,  es- 
pecially one  with  plain  and  deep  fillets  at  the  sides. 
Three  methods  are  here  given  for  running  double  dimin- 
ished mouldings  on  domes,  cupolas,  or  vaulted  ceilings, 
or  on  lower  surfaces.  These  methods  give  good  results, 
especially  if  a  little  thought  for  the  requirements  of  the 
case  is  bestowed  on  the  designing  of  the  moulding. 

Double  Diminished  Mouldings,  False  Screed  Method,-- 
By  this  method  the  diminish  in  depth  is  obtained  by  false 
screeds,  and  the  diminish  in  width  by  the  aid  of  a  dimin- 
ished rule,  which  is  fixed  on  the  centre  of  the  profile  or 
bed  of  enrichment.  This  method  is  elucidated  in  the  fol- 
lowing illustrations.  The  annexed  illustration  No.  15, 
shows  the  section  of  a  vertical  moulding  on  the  plaster 
or  floated  surface  of  the  inside  of  a  dome,  C  is  the 
main  cornice  from,  which  the  inner  line  of  the  dome 
springs.  The  D's  are  dots  which  are  used  to  regulate 
the -diminish  of  the  false  screeds.  The  various  thickness- 
es and  positions  of  the  dots  are  obtained  by  setting  out 


METHODS  OF  WORK 


205 


the  full  size  of  the  section  on  a  floor  or  worked  out  to  a 
scale.  If  the  section  is  elliptical,  dots  should  be  placed 
at  the  points  where  the  transition  of  curves  takes  place. 
When  the  surface  of  the  dome  has  been  floated^  the 
diminishing  dots,  D,  are  placed  at  each  side  of  the  in- 
tended moulding:  and  at  their  prbper  positions,  begin- 


•Section  ^Double  Diminished  Mouldings— 
False  Screed  Method. 

NO.  15. 


ning  above  the  main  cornice,  C,  and  going  upwards  m 
rotation  but  having  no  dot  at  the  top.  The  spaces  be- 
tween the  dots  are  next  filled  and  ruled  in,  bearing  on 
the  various  dots  with  the  curved  rules  or  templates. 
When  ruling  the  top  bay  of  the  screed,  the  top  end  of 
the  rule  bears  on  the  original  floating  at  the  top  or  ex- 


METHODS  OF  WORK 


207 


treme  point,  this  point  being  the  true  thickness  of  the 
screed. 

Illustration  No.  16  shows  the  plan  and  elevation  of  the 
work.  Fig.  1  shows  it  in  progress,  and  Fig.  2  when 
finished.  The  A's  on  plan  and  elevation  (Fig.  1)  are 
false  screeds,  the  B's  are  brackets,  while  C  C  indicates 
the  diminished  running  rule.  This  rule  is  made  as  fol- 
low^s: — First  plane  one  face  of  a  pine  board  about  % 
inch  thick,  and  of  sufficient  length  and  w^idth  for  the 
desired  purpose.  On  this  make  a  centre  line  from  end 
to  end.  From  this  centre  line  set  off  the  width  at  one 
end,  and  the  diminished  width  at  the  other  end ;  then 
extend  the  diminished  width  lines  from  end  to  end,  and 
then  plane  the  running  edges  to  the  diminished  lines.  In 
order  to  allow  the  rule  to  bend  freely  to  the  curved 
surface,  make  a  series  of  saw-cuts  crossways  on  the  back 
or  bed  face.  The  false  screeds  are  made  as  already  de- 
scribed. A  centre  screed  for  the  running  rule  is  made 
by  the  aid  of  a  template.  This  is  made  with  two  slippers, 
one  on  each  side,  similar  to  a  running  mould,  so  as  to  run 
on  the  false  screeds,  the  centre  or  cutting  edge  of  the 
template  being  made  to  the  depth  of  the  proposed  screed. 
The  face  surface  of  the  bracket  is  then  laid  with  gauged 
stuff  and  finished  off  by  working  the  template  up  and 
down.  This  done,  fix  the  diminished  rule,  C,  on  the 
centre  of  the  screed.  The  running  mould,  E,  on  the 
plan  is  made  with  the  slippers,  one  to  bear  on  the  centre 
screed  and  against  the  running  rule,  and  the  other  to 
bear  on  the  side  false  screed.  The  slippers  are  made 
circular  on  their  running  edges,  so  as  to  fit  the  circular 
screeds.  A  short  slipper  at  the  nib  gives  more  freedom 
and  ease  when  running  the  moulding,  and  the  mould  is 
not  so  liable  to  cut  up  the  screeds.  After  the  moulding 
is  run  on  both  sides,  take  the  running  rule  off,  then  cut 


208  CEMENTS  AND  CONCRETES 


the  false  screeds  down  to  the  floating;,  and  make  the  sides 
of  the  fillet  good,  and  then  fix  the  enrichment.  Fig.  2 
shows  the  plan  and  elevation  of  the  finished  moulding; 
and  enrichment.  A,  on  the  plan,  shows  one  side  of  the 
moulding  before  the  false  screed  is  cut  off,  and  G  show^s 
the  screed  cut  off  and  the  member  made  good  to  the 
floating.  The  amount  of  diminish  from  the  bottom  to 
the  top  of  the  moulding  is  shown  at  the  brackets  B  and 
B,  and  by  the  profiles  of  the  cornice  on  the  plan  and  ele- 
vation. The  bed  and  section  of  the  enrichment  is  shown 
at  F  on  the  plan.  As  tliis  enrichment  is  diminished  (in 
width  and  projection)  the  whole  length  must  be 
modelled. 

Running  Double  Diminished  Mouldings^  Diminished 
Ride  Method.i — This  is  a  method  which  is  introduced, 
and  is  somewhat  similar  to  the  first  method  described.  It 
is  well  adapted  for  running  mouldings,  having  no  en- 
richment on  the  centre  of  the  section,  the  bed  of  which 
may  be  used  as  a  screed  and  bed  for  a  running  rule,  as 
used  for  the  first  method.  By  this  method  the  whole 
moulding  is  run  in  one  operation.  The  diminish  in 
depth  is  obtained  by  the  use  of  two  running  rules 
diminished  on  the  face,  or  in  other  words.,  diminished 
in  thicknesSi.  The  diminish  in  the  thickness  of  the 
rules  is  obtained  by  setting  the  full  size,  as  described  for 
the  false  screeds  in  the  first  method.  A  series  of  saw- 
cuts  must  be  made  on  the  backs  of  the  rules  to  allow  them 
to  bend  to  the  circular  surface  of  the  dome.  These 
rules  act  in  a  similar  way  to  the  false  screed  used  in  the 
first  method,  with  the  addition  that  they  form  the  fillets 
of  the  outside  members,  thus  avoiding  cutting  the  screeds 
down  and  making  good  the  fillets.  They  are  also  used  for 
obtaining  the  diminish  in  width.  This  is  effected  by 
first  making  a  central  line  on  the  bed  surface  of  the 


METHODS  OF  WORK 


209 


proposed  moulding ;  then  from  this  line,  at  each  side,  set 
out  the  half  width  of  the  moulding,  including  the  bear- 
ing parts  of  the  running  mould.  This  is  done  at  the 
widest  or  bottom  end  of  the  moulding,  and  at  the  nar- 
rowest or  top  end.  Then  from  these  width  marks,  lines 
are  extended  from  end  to  end.  On  these  lines,  nails  are 
inserted  from  2  to  3  feet  apart,  which  act  as  guides  for 
fixing  the  running  rules.  The  inner  sides  of  the  rule  are 
placed  against  the  outer  sides  of  the  nails  and  fixed,  and 
then  the  guide  nails  are  extracted,  thus  forming  the 
diminished  space  and  bearings.  A  triple-hinged  mould 
with  a  slipper  at  each  side  is  used,  so  that  it  will  close  up 
while  being  run  up  the  diminished  space.  The  stock  is 
rebated,  so  that  it  will  run  on  the  tops  and  inner  sides 
of  the  rules.  The  mould  plate  must  be  cut  to  fit  the 
section  at  the  greatest  width  of  the  moulding,  but  care 
must  be  taken  that  the  depth  at  the  outer  members  is 
the  same  as  proposed  for  the  top.  The  ends  of  the  inner 
slippers  and  the  adjoining  parts  of  the  stock  are  cut 
so  as  to  leave  an  open  space,  to  allow  both  parts  to  work 
freely  when  the  mould  assumes  a  raking  position,  as 
shown  on  illustratiort  No.  17. 

The  extra  depth  of  the  square  of  the  outside  members 
is  formed  by  the  running  rules.  It  may  here  be  re- 
marked that  the  thickness  of  the  rules  at  the  top  should 
be  made  about  %  i^ich  thicker  than  the  depth  of  the 
square  part  of  the  outside  members.  For  example,  if 
the  depth  of  the  fillets  or  square  part  of  the  outside 
members  is  1  inch,  the  rules  should  be  II/2  inches  thick 
at  the  top.  This  allows  for  the  requisite  bearing  for  the 
running  mould.  The  ends  of  the  stock  that  bear  on  the 
inside  of  the  rules  must  be  rounded  off  to  allow  the 
mould  to  run  freely  when  it  closes  up  while  being  run 
up  between  the  dimipished  space. 


210  CEMENTS  AND  CONCRETES 


The  various  parts  of  the  running  mould  are  shown  in 
the  annexed  illustration  No.  17.  Fig.  1  shows  the  mould 


Diminished  Rule  Method. 

NO.  17. 

in  position  at  the  bottom  or  widest  part  of  the  moulding ; 
R,  are  sections  of  the  running  rulesj.  S,  S,  the  slip- 


METHODS  OF  WORK 


211 


pers;  and  H,  the  hinges  which  connect  the  two 
halves  of  the  stock  to  the  slippers.  The  hinge  which 
connects  the  mould  in  the  centre  is  fixed  on  the  other 
side  of  the  stock.  Its  position  is  indicated  by  dotted 
lines.  Fig.  2  shows  the  form  of  the  mould  when  at  the 
top  of  the  moulding.  The  letters  correspond  with  those 
on  Fig.  1.  The  thin  seams  at  the  centre  and  sides  of  the 
moulding  which  are  caused  by  the  joint  of  the  mould  in 
the  centre  and  by  the  joint  of  the  mould  and  the  rules 
are  cleaned  off  by  hand.  This  method,  like  the  first,  has 
the  defect  that  the  actual  diminish  or  the  whole  depth  of 
diminish  lies  in  the  fillets  of  the  outside  members  of  the 
.  moulding.  The  difference  between  the  diminished  mem- 
beris  and  the  regular  members  will  be  most  noticeable  on 
the  adjoining  members,  the  vertical  fillets  of  the  cavettos. 
If  this  defect  should  prove  offensive  to  the  eye,  it  may  to 
some  extent  be  remedied  by  working  these  members  down 
by  hand,  with  the  aid  of  planes,  gouges,  drags,  and  joint 
rules,  after  the  moulding  is  run,  so  as  to  reduce  the  depth 
of  the  fillets,  and  throw  the  difference  into  the  cavettos. 
A  line  should  be  set  out  to  the  desired  diminish  on  the 
.  fillets  to  act  as  guides  when  working  the  cavettos  down. 
Running  Double  Diminished  Mouldings^  Top  Rule 
Method. — Kunning  double  diminished  mouldings  by  the 
aid  of  a  '  ^  top  rule ' '  is  another  method  that  I  have  intro- 
duced for  this  purpose.  The  diminish  in  width  is  ob- 
tained by  fixing  two  slipper  running  rules  to  the  de- 
sired diminish  and  a  triple-hinged  mould  ais  previously 
described,  and  as  shown  at  Figs.  1  and  2  on  the  an- 
nexed illustration.  No.  18.  Fig.  1  shows  the  running 
mould,  M,  and  the  slipper  rules,  R,  R,  at  the  full-sized 
or  springing  end  of  the  moulding,  and  Fig.  2  shows  the 
running  mould  and  rules  at  the  diminished  end.  The 
dimiiaishing  depth  is  obtained  by  the  aid  of  a  ''top  rule'' 


212  CEMENTS  AND  CONCRETES 


which  is  fixed  on  two  blocks,  one  at  each  end  of  the 
moulding,  as  shown  at  Fig.  3.    This  shows  the  elevation 


Elevations,  Plan,  and  Sections  of 
•Running  Mould  and  Rules  for  Diminished 
Mouldings— Top-Rule  Method. 

NO.  18. 

of  one  side  of  the  running  moulds  at  the  springing  and 
diminished  ends  of  the  moulding,  also  the  running  rules. 


METHODS  OF  WORK 


213 


B  is  the  section  of  the  fixing  block  at  the  springing  end 
of  the  moulding,  and  D  is  the  fixing  block  at  the  dimin- 
ished end,  upon  which  the  top  rule,  T,  is  fixed.  This 
rule  is  fixed  on  the  slant,  to  suit  the  desired  diminish. 
It  must  be  made  sufficiently  wide  to  allow  a  bearing  for 
a  part  of  each  half  of  the  stock,  M,  M,  of  the  running 
mould,  and  also  fixed  over  the  joints  of  the  mould,  as 
shown  at  T,  Figs.  1,  2,  and  3.  The  top  rule  being  fixed 
on  the  slant,  causes  the  running  mould  to  gradually  cant 
over  when  it  is  drawn  from  its  upright  position  at  the 
springing  end  of  the  moulding  to  the  diminished  end, 
as  shown  at  Fig.  3,  thus  forming  the  diminish  in  the 
depth  of  the  moulding.  M  a  shows  the  end  section  of 
the  stock  in  an  upright  position  when  at  the  springing 
end,  and  M  is  the  section  of  th.e  stock  in  a  slanting  posi- 
tion when  at  the  diminished  ends  of  the  moulding.  The 
dotted  lines  in  both  indicate  the  parts  of  the  stocks  in- 
side the  slippers,  and  the  angular  dotted  line  at  H,  H, 
indicates  the  splayed  or  cut  side  of  the  hinge.  S  S  is 
the  outer  elevation  of  one  slipper  when  at  each  end  of 
the  moulding,  and  R  is  the  slipper  running  rule.  It 
yvill  be  seen  that  the  running  mould  at  Fig.  1  is  some- 
what similar  to  the  triple-hinged  running  moulds  pre- 
viously described.  But  there  are  two  important  excep- 
tions, namely,  the  hinges  at  the  centre  and  the  two  sides 
of  the  mould. 

The  side  hinges  for  this  mould  must  be  cut  on  one  side 
and  the  angles  rounded  off,  leaving  only  one  screw-hole, 
so  as  to  cause  less  friction,  and  allow  this  part  of  the 
hinge  to  turn  on  a  screw  when  fixed  on  the  slipper.  The 
use  of  this  will  be  seen  hereafter.  An  elevation  of  a 
hinge,  before  and  after  it  is  cut,  is  shown  at  Fig.  4.  The 
lower  hole  on  the  cut  half  of  the  hinge  is  used,  because 
the  nearer  the  ^ burning  points"  or  pivots  are  to  the 


214  CEMENTS  AND  CONCRETES 


running  ground  or  screed,  as  the  case  may  be,  the  less 
will  the  bearing  edges  of  the  running  mould  rise  when 
the  mould  cants  over.  For  instance,  if  the  ^'turning 
points''  were  made  at  the  centre  of  the  'depth  of  the 
mould,  the  bearing  edge  of  the  mould  would  rise  from 
the  ground  in  proportion  to  the  cant  of  the  stock.  This 
would  increase  the  depth  of  the  lower  members  (those 
below  the  pivots  or  turning  points),  instead  of  dimin- 
ishing them.  This  hole  must  be  enlarged  so  as  to  admit 
of  a  short  thick  screw  to  give  the  necessary  strength.  It 
will  be  understood  that  this  part  of  the  hinge  works  on 
the  plain  part  at  the  head  of  the  screw. 

Having  cut  the  right  and  left  hinges,  they  are  screwed 
on  to  the  stock  and  the  slippers  of  the  running  mould, 
keeping  the  half  of  the  hinge  with  the  three  screw-holes 
on  the  stock,  and  the  cut  part  with  one  screw-hole  on 
the  slippers,  as  shown  at  H,  H,  Fig.  1.  It  will  also  be 
noticed  that  these  hinges  are  fixed  at  the  lower  edge  of 
the  mould.  This  is  done  so  as  to  allow  the  stock  of  the 
mould  to  cant  from  its  basie  for  the  reason  already  men- 
tioned. When  screwing  the  cut  side  of  the  plate  to  the 
slipper,  allow  just  sufficient  play  for  the  hinge  to  turn 
smoothly  but  firmly  on  the  screw.  The  centre  hinge  con- 
necting the  halves  of  the  stock,  M,  M,  is  formed  with  two 
pieces  of  metal  plate.  The  inner  ends  are  rounded  off 
to  allow  them  to  turn  and  a  circular  orifice  one-third  the 
wddth  of  the  plate  is  drilled  at  the  circular  ends,  and 
then  three  or  more  screw-holes  for  fixing  purposes  are 
drilled  on  the  other  ends.  The  two  plates  are  fastened 
together  with  a  flat  metal  ring  or  with  stout  copper  wire. 
The  thickness  of  this  ring  is  regulated  according  to  the 
size  of  the  orifice,  but  allowing  just  sufficient  play  for 
the  plates  to  turn  both  ways  when  the  mould  assumes  a 
slanting  and  an  angular  position,  as  shown  at  Fig.  2. 


METHODS  OF  WORK 


215 


An  enlarged  view  of  the  centre  hinge  is  shown  at  Fig.  5. 
The  centre  hinge  is  screwed  on  the  inner  side  or  profile 
of  the  stock,  as  shown  at  C,  Fig.  1.  An  enlarged  view 
of  part  of  the  stock  at  the  joint,  when  inverted  for  fix- 
ing the  centre  hinge,  is  shown  at  Fig.  6.  The  top  and 
bottom  edges- and  the  ends  of  the  stock  must  be  rounded 
off,  to  allow  it  to  cant  over  easily.  The  diminish  of  this 
moulding,  both  in  depth  and  width,  as  shown  in  the  illus- 
tration, is  a  little  more  than  may  generally  occur  in  prac- 
tice, but  this  is  given  to  show  the  various  parts  more 
clearly,  also  what  to  avoid  in  the  amount  of  diminish 
when  using  this  method. 

The  diminishing  depth  here  shown  is  about  two-fifths, 
and  the  diminishing  width  about  one-third.  The  dimin- 
ishing depth,  by  this  method,  should  not  be  overdone, 
because  the  running  mould  assumes  an  angular  position 
both  on  plan  and  section,  therefore  it  forms  the  vertical 
parts  of  the  members  in  a  slanting  line  and  the  horizon- 
tal parts  out  of  a  level.  These  defects  become  more  pro- 
nounced at  the  diminished  end  of  the  moulding,  as 
shown  at  Fig.  2.  The  top  member  can  easily  be  made 
level  and  fair  by  hand,  but  it  would  entail  too  much 
labor  to  rectify  the  defects  of  the  other  members,  there- 
fore this  method  should  only  be  used  for  smal]  mould- 
ings or  where  the  diminish  in  depth  is  of  a  slight  nature. 
The  seam  at  the  top  member,  caused  by  the  joint  of  the 
mould,  is  cleaned  off  and  made  good  by  hand. 

Cupola  Panels  and  Mouldings. — In  order  to  facilitate 
the  setting  out  and  formation  of  cupola  panels  and 
mouldings,  the  method  of  drawing  them  is  given.  This 
will  be  found  very  useful  in  the  general  setting  out  and 
construction  of  cupolas,  whether  in  ''solid"  or  in 
''fibrous  plaster.''  Various  parts  of  cupolas  and  soffits 
of  arches  (from  designs  by  J.  Gibbs,  architect,  a  pupil 


216  CEMENTS  AND  CONCRETES 


of  Wren,  and  a  great  patron  of  the  plasterer's  art),  with 
the  method  of  drawing  same,  are  illustrated  on  plate  11. 
To  draw  an  octagonal  cupola,  as  shown  by  the  plan  at 
Fig.  1,  take  A  B  (the  width  of  one  side  of  the  octagon) 
as  the  base  line.  From  the  centre  of  this  erect  the  per- 
pendicular line  D  C,  then  draw  the  lines  C  A  and  C  B ; 
this  will  give  the  triangle  ABC,  forming  the  plan  of 
an  eighth  part  of  the  cupola.  The  profile  (Fig.  2)  is 
made  by  the  quadrant  of  circle  (ABC)  directly  over 
the  plan.  Divide  half  the  base  line,  A  B  on  plan,  into 
seven  parts,  as  here  figured,  and  six  of  them  will  make 
two  panels ;  the  seventh  will  remain  for  the  border.  The 
same  divisions  must  be  marked  on  the  profile  over  the 
line  A  B,  as  follows: — Take  for  the  border  at  the  bot- 
tom four  parts,  as  shown  in  the  plan ;  place  them  on  the 
profile  from  the  base  line  to  No.  1,  and  draw  a  line  par- 
allel to  the  base  line  of  the  plan;  measure  the  length  of 
the  two  central  lines  marked  2  2,  and  place  it  in  the 
profile  for  the  second  panel.  From  thence  draw  another 
parallel  line,  and  measure  the  length  of  the  two  central 
lines  at  3  3  in  the  plan  to  find  the  square  height  of  the 
third  panel,  and  so  on  to  No.  8,  as  shown  in  the  plan 
and  profile. 

The  elevation  or  upright  side  of  this  octagonal  cupola 
(Fig.  3)  is  made  by  the  following  geometrical  rule. 
First  draw  the  base  line  (A  B)  on  plan  even  with  the 
base  line  (A  B)  of  the  profile;  on  this  erect  the  perpen- 
dicular line  (DC)  for  the  centre  of  the  side;  then  draw 
all  the  parallel  lines  as  shown  by  G  G,  etc.  Take  half 
the  length  of  each  line,  figured  in  the  plan,  and  mark  it 
on  each  side  of  the  middle  line  of  Fig.  3  until  the  length 
of  every  panel  is  fixed.  From  these  lines  and  points  the 
forms  or  outlines  of  the  panels  are  taken.  The  inner 
divisions  are  brought  over  to  the  number  of  panels  con- 


7^ 


METHODS  OF  WORK 


217 


tained  therein  in  the  same  manner  as  they  appear  in 
Fig.  3.  The  same  rule  is  used  for  setting  the  side  shown 
at  Fig.  4. 

With  regards  to  the  soffits  of  arches,  if  they  are 
divided  into  panels,  they  must  be  of  any  uneven  number, 
as  shown  at  K  and  L,  by  having  a  panel  in  the  centre. 
The  border  must  not  be  more  than  one-sixth  nor  less 
than  one-seventh  part  of  the  whole  breadth.  The  quad- 
rant or  profile,  E  F  (Fig.  2),  on  which  the  panels  of  this 
semi-circular  soffit  are  divided,  will  be  sufficient  to  ex- 
plain them.  A  circular  soffit  of  lesser  breadth  is  shown 
at  M,  and  one  of  greater  breadth  is  shown  at  N.  Sec- 
tions of  each  soffit  are  shown  at  the  top  of  the  eleva- 
tions. 

The  method  of  constructing  the  plaster  work  of  cupo- 
las depends  to  some  extent  on  the  design  and  size  of  the 
panels  and  mouldings.  For  example,  if  the  diagonal 
panels  shown  in  Fig.  3  were  sufficiently  large  to  admit 
of  a  running  mould  to  run  a  piece  of  moulding  (on  each 
side  of  the  panels)  not  less  in  length  than  the  mitres  at 
each  end,  the  best  method  would  be  to  run  the  four  sides 
of  all  the  panels;  but  if  the  panels  were  too  small  to 
allow  a  running  mould  to  run  the  requisite  amount  of 
moulding,  it  would  be  necessary  to  run  a  part,  and  cast, 
or  run  down,  and  plant  the  other  parts.  In  some  designs 
it  would  be  necessary  to  plant  all  the  mouldings.  In 
some  cases  the  panel  mouldings,  from  the  base  up  to  a 
third  or  fourth  of  the  height  of  the  cupola,  can  be  con- 
veniently run;  but  the  panels  above  this  which  become 
smaller,  and  are  too  small  to  admit  of  their  being  run 
with  economy,  should  be  planted.  Another  method  is 
to  run  all  the  diagonal  mouldings  that  spring  from  left 
to  right,  as  from  A  to  a,  in  one  length  from  border  to 


218  CEMENTS  AND  CONCRETES 


border,  and  then  run  the  intermediate  parts  of  the 
mouldings  springing  from  right  to  left. 

The  intermediate  parts  may  also  be  run  down,  or  cast, 
and  then  planted.  By  this  method  the  intermediate 
parts  only  require  mitring,  and  if  they  are  planted  the 
intersections  only  require  to  be  stopped.  If  these  parts 
are  run,  the  brackets  from  right  to  left  must  be  cut 
down  at  the  intersections  to  allow  the  running  mould  to 
pass  when  running  the  mouldings  from  left  to  right  in 
one  length.  Whichever  method  is  employed,  the  surface 
must  be  floated  true  to  the  various  curves  to  form  a 
ground  for  the  mouldings,  whether  run  or  slanted.  The 
surface  should  also  be  floated  sufficiently  smooth  to  act 
as  screeds  without  using  gauged  putty  screeds  for  each 
moulding.  This  is  done  as  described  for  panelled  ceil- 
ings. The  groundwork  of  the  floating  is  effected  by  first 
forming  a  screed  on  the  base  border  (A  B),  and  one  on 
the  top  border  (at  C),  and  then  from  these  screeds  as 
bearings,  form  two  screeds  on  the  side  or  vertical  bor- 
ders, thus  completing  the  main  screeds,  and  from  which 
the  panel  surface  is  floated.  Owing  to  the  brackets  and 
the  form  of  the  panels,  it  is  a  somewhat  difficult  opera- 
tion to  float  all  the  panel  surfaces  with  a  uniform  depth 
and  curve.  It  will  be  seen  that  a  floating  rule  (cut  or 
so  constructed  to  clear  the  brackets),  whether  worked 
vertically  or  horizontally,  cannot  travel  into  the  angles, 
and  float  the  whole  surface.  This  difficulty  is  overcome 
by  making  dots  in  each  angle,  or  making  narrow  screeds 
from  angle  to  angle  of  each  panel.  The  horizontal  dots 
or  screeds,  as  the  case  may  be,  are  ruled  off  with  a  gauge 
rule,  which  is  cut  to  the  required  depth,  and  to  bear  on 
the  side  screeds.  The  vertical  screeds  are  ruled  off  with 
the  circular  rule,  on  which  pieces  of  board  cut  to  the 
desired  depth  and  length  of  the  various  panels  have  been 


METHODS  OF  WORK 


219 


previously  fixed.  The  intervening  spaces  are  then  ruled 
off  with  short  rules  cut  to  the  angular  curves. 

Another  and  better  way  is  to  cut  an  angular  floating 
rule  to  fit  the  curve  from  A  to  a,  and  float  all  the  panel 
surfaces  in  a  line  from  border  to  border  in  one  opera- 
tion. This  angular  rule  is  set  out  in  a  similar  way  as 
described  for  angle  brackets.  The  rules  for  this  or  the 
first  method  must  be  made  to  suit  the  longest  line  or 
set  of  panels.  After  each  set  of  corresponding  panels 
in  the  other  sides  of  the  cupola  is  floated,  they  must  be 
shortened  to  fit  the  next  set  of  panels,  and  so  on,  until 
all  the  panels  are  floated.  The  mouldings  being  dimin- 
ished in  width,  are  run  from  a  diminished  running  rule 
fixed  on  a  centre  screed  in  the  same  way  as  described  for 
diminished  dome  mouldings.  The  screed  for  this  method 
is  formed  by  an  angular  floating  rule  cut  to  the  angular 
curve,  as  already  mentioned.  For  some  designs  the 
moulding  may  be  run  with  a  twin-slippered  running 
mould.  This  form  of  mould  can  also  be  used  for  form- 
ing about  one  inch  of  the  panel  surface.  This  acts  as 
a  ground  for  floating  the  panel  surfaces.  When  large 
paterae  are  used,  the  ground  panel  surface  may  be  cast 
with  them,  thus  avoiding  floating  and  setting.  The  oc- 
tagonal panels  shown  in  Fig.  4  are  formed  in  a  similar 
way  to  Fig.  1.  After  the  vertical  and  horizontal  mould- 
ings are  run,  the  diagonal  sides  of  the  octagons  are 
planted.  Where  square  panels  form  the  design,  the 
mouldings  can  be  run  with  a  radius-rod  running  mould 
from  a  centre  pin  and  block.  The  sections  of  the  soffits 
of  the  arches  are  run  with  a  radius-rod  running  mould, 
fixed  on  a  radius  boards  and  the  cross  styles  or  mould- 
ings, as  shown  at  K  and  L,  are  planted.  A  small  portion 
of  the  arch  should  be  run  to  form  a  ground  on  which  the 


220  CEMENTS  AND  CONCRETES 


enrichments  may  be  modelled.  Fibrous  plaster  is  well 
adapted  for  constructing  the  plaster  lining  of  cupolas. 

Panelled  Beams, — When  panelled  beams  have  mould- 
ings on  the  lower  part  of  their  sides  or  faces,  and  on  the 
soffit  to  form  a  sunk  panel,  they  may  be  run  in  two  parts. 
Screeds  are  formed  on  the  two  sides,  and  one  in  the 
centre  of  the  soffit.  If  the  mouldings  on  the  sides  have 
more  girth  or  are  larger  than  the  portion  on  the  soffit, 
they  may  be  run  from  rules  fixed  on  the  side  of  the  beam, 
with  the  nib  bearing  on  the  style  or  on  the  soffits.  If 
the  style  and  mouldings  on  the  soffit  are  small,  the  mould 
is  made  to  run  the  face,  style,  and  soffit  moulding  in  one. 
If  the  styles  are  broad,  the  moulding  on  the  sunk  part 
of  the  soffit  is  run  from  a  parallel  running  rule  fixed  in 
the  centre  of  the  soffit,  thus  forming  a  double  rule  to  run 
each  side  of  the  sunk  moulding.  The  latter  way  is  most 
generally  used.  The  end  or  other  mouldings  required 
for  panelling  the  soffit  are  run  down  and  planted. 

All  beams  of  any  length  should  always  have  a  camber, 
not  only  to  allow  for  any  settlement  that  may  take  place, 
but  to  make  it  more  pleasing  to  the  eye.  A  beam  dead 
level  and  straight  has  the  appearance  of  sagging  in  the 
centre.    This  may  be  termed  an  optical  illusion. 

Trammels  for  Elliptical  Mouldings, — It  may  at  once 
be  pointed  out  that  an  ellipse  and  an  oval  are  not  the 
same.  Both  ends  of  an  ellipse  are  similar,  and  an  oval 
is  egg-shaped,  one  end  having  a  greater  curve  than  the 
other,  therefore  the  term  oval  moulding  or  panel  is 
scarcely  correct  when  applied  to  the  following  illustra- 
tions. This  term,  however,  is  be^st  known  and  generally 
used  by  most  workmen  in  the  building  trades.  The  term 
^'ellipticar'  is  generally  applied  by  plasterers  when  re- 
ferring to  mouldings  where  the  whole  ellipse  is  not  car- 
ried round,  such  as  for  mouldings  or  elliptical  arches, 


METHODS  OF  WORK 


221 


windows,  etc.;  and  the  term  ''oval/'  where  the  whole 
figure  is  completed,  such  as  panels  (elliptical  on  plan  J 
formed  on  walls  or  ceilings.  In  consideration  of  the 
common  usage  of  these  terms,  they  will  here  be  used  in 
describing  the  setting  out  or  v/orking  of  same. 

Trammels  are  often  used  for  tunning  oval  panel 
mouldings,  and  for  forming  the  lines  when  setting  out 
oval  templates.  Trammels  are  made  of  wood  or  metal. 
A  simple  way  to  make  a  tram- 
mel for  small  work  is  to  sink 
two  grooves  at  right  angles  in 
a  hardwood  board  (termed  the 
plate),  about  7  inches  long, 
5  inches  wide,  and  1  inch 
thick.  The  grooves  are  about 
1-2  inch  deep  and  1-2  inch 
wide.  Two  hardwood  pins  are 
then  made  to  fit  the  grooves. 
They  have  collars  to  bear  on 
the  surface  of  the  plate.  The 
upper  part  is  made  round  to 
fit  the  centre  holes  of  the  rod. 
The  subjoined  illustration  No. 
19  shows  a  template  and 
various  sorts  of  template  pins. 
Fig.  1  is  a  view  of  a  template, 
with  the  two  pins,  rod,  with  the 
running   mould   attached  in 

position,  and  a  part  of  a  moulding.  Fig.  2  shows  various  sec- 
tions of  pins.  A  is  the  section  of  the  pin  as  used  in  Fig.  1, 
and  C  is  the  plan  of  the  pin  at  the  intersection  of  the 
grooves.  B  is  the  section  of  a  dovetailed  pin  used  for 
another  form  of  trammel.  The  rod  is  made  to  any  de- 
sired length,  so  that  it  may  serve  for  various  sized  ovals. 


F14  I. 


^Trammels. 

NO.  19. 


222  CEMENTS  AND  CONCRETES 


The  average  size  for  this  kind  of  trammel  is  about  1  foot 
6  inches  long,  1  inch  wide,  and  1-4  inch  thick.  A  series 
of  holes  1-4  inch  in  diameter  (to  fit  the  head  of  the  pin) 
is  made  about  1-8  inch  apart  on  the  flat  side.  The  first 
hole  is  made  near  one  end  of  the  rod,  and  continued 
down  the  centre  for  about  15  inches^  leaving  the  blank 
space  for  screwing  on  to  the  running  mould.  A  pin  is 
now  laid  into  each  groove,  and  the  size  of  the  desired 
oval  is  obtained  by  regulating  the  length  of  the  rod  at 
each  diameter  by  means  of  the  holes.  The  pin  in  the 
short  groove  is  the  point  from  which  the  length  of  the 
oval  is  taken,  and  the  pin  in  the  long  groove  for  the 
width.  The  trammel  is  fixed  on  the  running  board  by 
means  of  two  or  more  screws,  as  shown.  This  size  of 
trammel  can  only  be  used  for  oval  mouldings  from  about 
10  inches  to  36  inches  at  their  longest  diameter,  there- 
fore larger  sizes  are  required  for  larger  ovals. 

A  trammel  for  running  large  ovals  (say  from  6  to  10 
feet  at  the  major  diameter),  if  made  solid,  as  shown  in 
Fig.  1,  would  be  too  heavy  and  cumbersome  for  fixing 
on  ceilings  where  the  mouldings  are  run  in  situ.  A 
lighter  kind  termed  a  cross"  template,  is  made  as  fol- 
lows:— Cut  three  fiooring  boards,  one  a  little  less  in 
length  than  the  longest  diameter  of  the  proposed  oval, 
and  two  less  than  the  short  diameter.  Lay  them  down 
on  a  floor  in  the  form  of  a  cross  (similar  to  the  grooves 
in  Fig.  1),  and  fix  and  brace  them  together.  Four  angu- 
lar braces  will  hold  them  together,  and  allow  the  whole 
to  be  fixed  on  the  ceiling.  On  the  centre  of  this  ground 
make  two  lines  at  right  angles  to  each  other,  and  from 
these  set  out  the  width  of  the  desired  grooves  at  the  ends 
and  intersections,  and  then  fix  wood  fillets,  each  about 
one  inch  thick  and  two  inches  wide,  to  the  marks,  thus 
forming  the  grooves.   In  order  to  prevent  the  pins  drop- 


METHODS  OF  WORK 


223 


ping  out  of  the  grooves  when  the  trammel  is  fixed  face 
downward  on  the  ceiling,  the  inner  sides  of  the  fillets 
should  be  splayed  so  as  to  receive  dovetailed  pins,  as 
shown  at  B,  Fig.  2.  This  may  also  be  effected  by  fixing 
running  rules  on  the  fillets  so  as  to  overlap  about  1-4 
inch,  over  the  groove  space,  thus  forming  rebated  or 
square  grooves.  The  pins  are  made  with  shoulders  to 
fit  the  grooves.  In  both  modes  a  1-inch  pin  must  be  in- 
serted in  the  trammel  pm  to  prevent  the  rod  dropping. 

A  strong,  accurate,  and  permanent  trammel  can  be 
constructed  entirely  with  metal.  To  make  this,  procure 
a  sufficient  length  of  metal  tube,  about  1-2  inch  in  diam- 
eter, having  a  slot  about  1-8  inch  wide,  cut  longitudi- 
nally. Cut  the  tube  into  four  pieces,  mitring  the  inter- 
sections, and  fix  and  brace  them  together  in  the  form  of 
a  cross,  as  already  mentioned.  A  pin  made  to  fit  the  slot, 
fixed  in  a  ball  made  to  fit  the  tube,  completes  one  of  the 
sliding  pins.  The  rod  may  be  made  of  metal  or  wood, 
but  the  latter  gives  more  freedom  for  changing  the  size 
for  different  sized  ovals. 

Various  methods  are  employed  for  running  oval  panel 
mouldings  on  ceilings.  The  most  useful  are  by  means  of 
trammels,  or  wood  or  plaster  templates.  A  trammel  is 
a  good  instrument  for  running  oval  panels  where  the 
mouldings  are  not  wide.  Wide  mouldings  (say  over  1 
foot)  cannot  be  run  true  or  uniform  in  width  in  one 
operation  with  a  trammel,  because  the  running  mould, 
which  is  fixed  on  the  end  of  the  rod  of  the  trammel, 
assumes  a  raking  position  when  it  is  between  the  right 
angle  points  of  the  major  and  minor  diameters  of  the 
oval.  This  raking  position  takes  place  at  the  four  joints 
or  change  of  curves  of  the  oval,  and  is  more  pronounced 
in  extra  wide  mouldings.  This  difficulty  is  overcome  by 
running  the  mouldings  in  two  parts,  using  a  trammel 


224  CEMENTS  AND  CONCRETES 


mould  for  running  the  first  or  inner  part,  and  a  run- 
ning mould  (horsed  to  run  on  the  run  part)  for  running 
the  second  or  outer  part.  This  is  effected  by  dividing 
the  section  of  the  moulding  into  two  parts,  taking  care 
to  make  the  joint  at  the  side  of  a  fillet  or  in  the  center 
of  a  flat  member  at  the  outer  side  of  the  part  to  be  run 
with  the  trammel  mould,  so  as  to  allow  for  a  good  bear- 
ing (wide  and  strong)  for  the  slipper  of  the  running 
mould  used  for  running  the  second  part.  The  running 
mould  for  the  first  part  is  fixed  on  the  rod  of  the  tram- 
mel as  already  mentioned.  The  running  mould  for  the 
second  part  is  horsed  with  a  circular  slipper  cut  to  fit 
the  curve  of  the  first  moulding.  If  the  oval  has  quick 
curves,  a  slipper  with  two  pins  will  give  the  best  re- 
sults. 

If  there  is  an  enrichment  in  or  near  the  center  of  the 
moulding,  run  the  moulding  in  three  parts,  using  the 
bed  of  the  enrichment  (which  is  run  with  a  trammel 
mould)  as  a  center  running  rule  for  running  the  outer 
and  inner  parts,  which  are  run  with  circular  or  pin- 
slippered  running  moulds,  as  already  described.  It  will 
be  seen  that  by  using  either  of  these  three  methods,  wide 
mouldings  for  oval  panels  can  be  run  uniform  on  width ; 
the  trammel  mould  giving  the  form  of  the  oval  to  the 
fi.rst  part  of  the  moulding,  or  to  the  center  running  rule, 
and  the  curved  slippered  running  moulds  giving  the  de- 
sired uniformity  of  width  to  the  full  section  of  the 
moulding.  Most  forms  of  oval  panel  mouldings  are  best 
run  with  templates.  When  run  with  trammels,  or  with 
radius-rods,  the  running  mould  is  apt  to  jump  and  cause 
cripples  at  the  junction  of  the  major  and  minor  diam- 
eters. 

Templates  for  Running  Elliptical  Mouldings. — The 
true  form  of  an  ellipsis  can  only  be  derived  from  the 


METHODS  OP  WORK 


225 


diagonal  cut  from  the  cone  or  the  cylinder,  and  the  near- 
est approximation  to  this  curve  must  be  obtained  by 
continuous  motion.  There  is  no  other  instrument  so 
well  adapted  for  effecting  this  purpose  as  a  trammel. 
For  a  true  ellipsis,  make  the  distance  from  the  outer  end 
of  the  rod  to  the  nearest  point  or  centre  pin  equal  to 


Template  and  Pin-Mould  for  Running 
Elliptical  Arch  Mouldings. 

NO.  20. 


half  the  shortest  or  minor  diameter  of  the  ellipsis,  and 
from  the  centre  pin  to  the  outer  pin  equal  to  half  the 
longest  or  major  diameter.  This  shows  the  use  of  a 
trammel  for  setting  out  the  lines  to  make  a  template  for 
this  form  of  ellipsis. 

The  subjoined  illustration  No.  20  elucidates  the  method 
of  setting  out  another  form  of  ellipsis;  also  an  oval  hav- 


226  CEMENTS  AND  CONCRETES 


ing  its  major  axis  one-third  greater  than  its  minor.  This 
also  shows  the  template  and  a  pin  running  mould  in  posi- 
tion for  running  an  elliptical  arch  moulding.  The 
template  (Fig.  1)  is  made  to  extend  below  the  springing 
line  of  the  arch,  so  as  to  allow  the  mould  to  be  run  down 
to  the  spring  of  arch  and  save  mitring.  The  template 
for  running  the  arch  extends  to  the  shaded  part;  but 
to  utilize  the  space  the  curve  has  been  continued  round 
to  show  a  method  of  setting  out  a  template  from  which 
an  oval  moulding  can  be  run,  the  oval  having  its  major 
axis  one-third  greater  than  its  minor.  The  method  of 
setting  out  is  as  follows:  First  draw  the  line  AB,  the 
greater  diameter,  to  the  desired  length;  then  bisect  it, 
and  erect  the  perpendicular  line  CD ;  this  being  the 
lesser  diameter,  is  made  a  third  less  than  the  line  AB. 
Then  bisect  each  half  of  the  line,  which  will  divide  the 
line  AB  into  four  equal  parts  and  give  the  centres  E,  E, 
which  are  the  centres  for  describing  the  ends,  as  from 
F  to  F,  and  Fl  to  F2.  Then  from  the  centres  C  and  D 
describe  the  flat  curves  from  F  to  Fl,  and  from  F  to  F2, 
which  complete  the  oval.  It  is,  however,  better  to  set 
out  this  template  by  the  trammel,  as  the  junction  of  the 
segments  of  the  circles  always  has  a  more  or  less  crip- 
pled look. 

Fig.  2  shows  a  pin-mould"  in  position  when  run- 
ning an  elliptical  arch  moulding.  This  mould  is  pro- 
vided with  two  hardwood  pins  inserted  into  the  bearing 
face  of  the  slipper.  The  pins  bear  on  the  edge  of  the 
template,  and  owing  to  their  position,  and  being  apart, 
allow  the  mould  to  take  any  change  of  curve  without 
*  ^jumping." 

Before  running  elliptical  mouldings  on  arches  or  win- 
dows, the  centres  and  running  rods  should  be  tested,  so 
.  that  the  mouldings  will  intersect  accurately,  and  so  avoid 


METHODS  OF  WORK 


227 


jumps  at  the  change  of  curves.  All  centre  pins  should 
be  level  with  each  other,  and  equidistant  from  the  centre 
of  the  arch  or  window.  The  outline  and  intersections  of 
the  proposed  moulding  can  be  tested  by  temporarily  fix- 
ing a  pencil  on  the  outer  and  inner  profiles  of  the  run- 
ning mould,  then  working  the  mould  over  the  screeds, 
so  that  the  pencils  will  form  two  lines.  I  have  heard  of 
a  three-centered  elliptical  hood  moulding  being  run  over 
a  window  with  what  is  called  a  ' '  bolt  radius-rod. ' '  This 
rod  i;s  made  in  two  parts  and  connected  with  a  hinge, 
and  held  straight  when  running  the  long  diameter  with 
a  bolt  and  sockets  where  fixed  at  the  joint.  The  run- 
ning mould  is  fixed  on  one  end,  and  a  centre  plate  on 
the  other  in  the  usual  way.  The  long  diameter  of  the 
moulding  is  run  first,  and  when  the  radius-rod  reaches 
the  change  of  curve  the  bolt  is  drawn  back,  and  the  short 
diameter  of  the  moulding  run  with  the  short  part  of  the 
radius-rod.  A  nail  is  inserted  in  a  board  which  is  pre- 
viously fixed  in  the  window  opening.  The  nail  must  be 
fixed  in  a  line  with  the  change  of  curve  so  as  to  stop 
the  radius-rod,  and  hold  the  long  part  in  position  while 
the  short  part  is  working.  The  same  operation  is  re- 
peated for  the  other  side  of  the  work.  It  is  needless  to 
say  that  this  method  is  far  too'  complicated  to  be  serv- 
iceable for  general  purposes. 

Templates  are  used  for  running  most  forms  of  ellip- 
tical panel  mouldings.  Plasterers  may  make  their  own 
templates  or  running  rules  by  using  fibrous  plaster  casts 
as  a  substitute  for  wood.  This  is  effected  by  first  set- 
ting out  a  quarter  of  the  proposed  oval  panel,  then  cut 
out  or  run  a  temporary  plaster  running  rule  to  fit  the 
inner  line,  allowing  a  space  for  the  slipper  of  a  running 
mould.  Cut  a  reverse  running  mould  to  the  section  of 
the  proposed  fibrous  plaster  rules  (say  about  1  inch  thick 


228  CEMENTS  AND  CONCRETES 


and  3  inches  wide),  then  run  the  quarter  length  of  the 
oval,  and  after  making  true  joints  at  the  ends,  cast  four 
fibrous  plaster  quarters,  and  then  lay  and  fix  them  re- 
versely, thus  completing  the  full  oval  template  or  run- 
ning rule.  The  full  oval  running  rule  can  also  be  run 
in  situ  and  in  one  operation.  This  may  be  done  with 
a  trammel  or  with  radius-rods,  according  to  the  form 
and  size  of  the  panel.  Strong  and  stiff  gauged  plaster 
or  a  strong  white  cement,  should  be  used  for  the  run- 
nixig  rule,  to  enable  it  to  resist  the  friction  of  the  run- 
ning mould  while  running  the  moulding.  Radius-rods 
are  more  often  used  for  setting  out  the  lines  for  oval  tem- 
plates than  for  running  the  mouldings.  Circular  mould- 
ings— vertical,  horizontal,  or  angular — run  off  circular 
grounds  require  special  running  rules,  so  that  they  will 
take  or  bend  to  the  double  curvature.  For  this  purpose^ 
cane,  flexible  metal  pipes,  and  wooden  rules,  having  series 
of  saw-cuts  on  the  backs  and  sides,  have  been  used,  but 
cast  fibrous  plaster  rules  or  a  jack  template  are  more 
suitable  for  most  of  these  purposes.  Template  can  also 
be  made  by  means  of  a  plasterer's  oval. 

Plaster er^s  Oval. — The  subjoined  illustration  (No.  21) 
elucidates  the  setting  out  of  this  form  of  oval  to  any 
given  size,  also  the  method  of  formi,ng  two  oval  mould- 
ings from  two  circle  mouldings.  The  ovals  are  formed 
by  running  two  circular  mouldings  in  plaster,  the  diam- 
eter of  one  being  exactly  double  that  of  the  other.  Each 
circle  is  cut  into  four  quadrants  or  quarters.  Two  of  the 
quadrants  of  the  larger  circle  form  the  sides  of  one  oval, 
and  two  quadrants  of  the  smaller  circle  form  the  ends, 
the  four  segments  making  a  fairly  good  oval.  The  re- 
maining segments  constitute  another  oval  of  similar  size 
and  shape.  The  method  is  simple  and  speedy,  and  it 
can  also  be  employed  for  the  formation  of  elliptical 


METHODS  OF  WOEK 


22S 


230  CEMENTS  AND  CONCRETES 


mouldings  on  arches,  doors,  or  windows  as  well  as  for 
oval  panel  mouldings.  The  formation  of  ovals  by  this 
method  has  been  employed  by  plasterers  for  genera- 
tions, but  owing  to  the  want  of  a  definite  rule  for  set- 
ting out  this  form  of  oval  to  any  given  size,  its  use  has 
been  somewhat  limited.  To  meet  this  want,  I  have  in- 
vented a  method  which  can  be  adopted  for  most  pur- 
poses, and  which  I  give  h^re  for  the  first  time.  For 
want  of  a  better  name  we  have  called  this  a  ''Plasterer's 
Oval, ' '  for  the  reason  that  plaster  lends  itself  more  read- 
ily than  any  other  material  to  the  formation  of  circular 
mouldings.  No  one  in  the  building  trades  can  form  a 
circle  or  an  oval  moulding  so  quickly  and  accurately  as 
a  plasterer.  The  method  of  setting  out  and  of  con- 
structing this  form  of  oval  is  as  follows :  To  set  out  an 
oval  to  a  given  size,  the  greater  diameter  being  given. 
Take  this  greater  diameter  as  a  base  to  determine  the 
required  diameters  of  the  large  and  small  circle  mould- 
ings, M  and  N,  Fig.  2.  Let  the  line  A  B,  Fig.  1,  be  the 
given  diameter,  say  3  feet;  on  this  form  two  squares, 
each  according  to  their  diameter  would  be  1  foot  6  inches 
by  1  foot  6  inches,  as  shown  at  C  D  E  F  and  F  G  H  C ; 
then  draw  diagonals  in  each  square  as  at  C  E  and  D  F 
and  C  G  and  F  H  and  at  their  intersections  1  and  1  as 
centres  draw  the  circles  1  K  and  1  K.  The  radius  in  this 
example  would  be  9  inches.  The  quadrants  M  and  M  1 
correspond  with  the  same  letters  in  Figs.  2  and  3,  and 
they  form  the  two  ends  of  the  oval.  After  this  take  C  as 
a  centre,  and  with  a  radius  from  C  to  0  at  E  or  G  de- 
scribe that  part  of  the  circle  L  from  0  L  0,  which  forms 
the  upper  side  of  the  oval ;  now  take  F  as  a  centre,  and 
with  the  same  radius  describe  the  lower  side,  joining  K  K 
at  0  and  0,  thus  forming  the  plan  of  the  oval  as  shown 
by  the  line  ALB,  and  the  dotted  line  below  C  It  will  be 


METHODS  OF  WORK 


231 


seen  that  the  respective  centres  to  describe  this  figure 
give  the  centres  and  diameters  to  run  the  two  circle 
mouldings  from  which  the  ovals  are  formed. 

To  construct  the  oval,  first  make  a  running  mould  to 
the  desired  profile,  using  a  radius-rod  in  the  usual  man- 
ner, for  running  circles  on  the  flat.  Before  running  the 
mouldings,  set  out  tw^o  lines  at  right  angles  on  the  mould- 
ing board,  taking  care  to  extend  the  lines  a  little  be- 
yond the  outline  of  the  large  circle,  as  shown  by  the 
dotted  lines  (Fig.  2).  The  extended  parts  of  these  lines 
act  as  guides  for  cutting  the  moulding  into  exact  quad- 
rants. The  intersection  of  them  is  the  centre  from 
which  both  circles  are  run.  Apply  the  running  mould, 
and  turn  it  round,  so  that  it  leaves  a  faint  mark  on  the 
running  board  to  indicate  the  width  of  the  moulding  to 
be  run.  The  width  can  also  be  marked  by  the  aid  of  a 
pencil,  holding  it  at  the  outside  member,  and  turning  the 
mould  round,  repeating  this  operation  on  the  inside  mem- 
ber. On  this  space  drive  in  eight  tacks,  two  in  each 
quadrant,  leaving  the  heads  projecting  about  %  inch. 
The  object  of  these  tacks  is  to  prevent  the  moulding 
from  lifting  owing  to  plaster  swelling,  or  from  moving 
round  while  being  run.  Cover  the  tacks  with  clay  to 
allow  the  moulding  to  be  freely  taken  up  after  it  is  run 
and  cut.  The  moulding  is  then  run  in  the  usual  way, 
and  is  cut  into  four  quarters,  or  quadrants.  This  is 
done  by  applying  two  set-squares,  one  inside  and  one 
outside  of  the  moulding ;  and  at  one  of  the  quarter  lines 
lay  a  straight-edge  over  the  moulding  and  against  the 
set-squares.  The  moulding  can  then  be  marked  or  sawn 
at  the  proper  place  and  angle.  The  dotted  or  quarter 
lines  divide  the  mouldings  into  quadrants,  and  give  the 
angles  for  cutting  them. 


232  CEMENTS  AND  CONCRETES 


The  use  of  extending  the  lines  beyond  the  moulding 
will  here  be  seen.  A  part  may  be  obliterated  while  the 
moulding  is  being  run,  bu.t  the  extended  part  will  af- 
ford a  correct  guide  for  the  outside  set-square.  If  the 
quadrants  are  cut  fine,  square,  and  clean,  the  joints  will 
be  scarcely  perceptible  when  the  four  segments  are 
placed  together.  When  this  circle  is  cut  and  taken  off 
the  board,  the  radius  has  to  be  altered  to  exactly  one- 
half  of  the  large  circle,  and  the  small  circle  is  run  and 
cut  precisely  in  the  same  way  as  the  large  one.  The  four 
quadrants  can  now  be  fixed  to  form  an  oval,  as  shown 
in  Fig.  3.  If  a  quantity  of  oval  mouldings  be  required, 
a  casting  mould  can  be  taken  off  this  oval  in  which  they 
may  be  cast.  It  will  be  seen  that  the  quadrants  M  and 
N  1  form  the  sides  of  the  oval  in  Fig.  3,  and  the  quad- 
rants M  and  M  1  form  the  ends.  It  will  also  be  seen  that 
after  completing  this  oval  there  are  four  quadrants  left 
to  form  another  oval.  If  but  one  oval  is  required,  run 
only  one-half  of  each  circle,  allowing  a  little  space 
beyond  the  centre  line,  so  that  a  square  and  clean  joint 
can  be  cut.  A  thin  saw  with  fine  small  teeth  should  be 
used  for  this  purpose. 

Fig.  3  shows  the  four  segments  of  the  moulding  in 
position  forming  the  oval.  In  this  figure  the  moulding 
is  struck  on  the  outside  of  the  setting-out  circle  line,  as 
shown  in  Fig.  1,  but  the  moulding  in  Fig.  2  is  struck  on 
the  inside  of  the  setting-out  lines.  This  is  simply  to 
show  that  the  same  centres  can  be  used  for  mouldings 
struck  on  either  side  of  the  lines.  A  mould  for  casting 
oval  mouldings,  also  templates,  can  also  be  made  by  the 
above  process.  For  this  purpose  a  reverse  running 
mould  must  be  used  for  running  the  two  circles.  A 
plaster  piece  mould  for  casting  oval  mouldings  that  are 
undercut  may  also  be  formed  by  this  method.    In  this 


METHODS  OP  WORK 


233 


case  the  running*  mould  must  be  made  and  used  as  de- 
scribed for  ' '  reverse  moulds. ' ' 

Coved  Ceilings. — Coves  to  ceilings  are  of  various 
heights,  as  one-third,  one-fourth,  one-fifth,  &c.,  of  the 
whole  height.  The  form  of  the  cove  is  generally  either 
a  quadrant  of  a  circle  or  of  an  ellipsis,  taking  its  rise  a 
little  above  the  cornice,  and  finishing  at  the  crown  or 
other  moulding.  If  the  room  is  low  in  proportion  to  its 
width,  the  cove  must  likewise  be  low;  and  when  it  is 
high,  the  cove  must  likewise  be  so;  by  which  means  the 
excess  of  height  will  be  rendered  less  perceptible.  An 
example  of  two  coved  ceilings  (from  designs  by  James 
Gibbs)  are  shown  is  the  annexed  illustration  No.  22. 
Fig.  1  shows  the  plan  and  elevation  of  a  coved  ceiling, 
with  circular  windows  between  the  groins.  Fig.  2  shows 
the  plan  and  elevation  of  a  coved  ceiling,  the  design  of 
which  is  less  intricate  than  that  of  Fig.  1.  The  curve 
of  this  cove  is  a  quadrant  of  a  circle,  as  shown  by  the 
section  at  the  side.  The  plans  will  enable  the  section 
of  each  design  to  be  understood,  and  vice  versa,  and  the 
whole  will  render  the  method  of  constructing  coves  and 
circular  mouldings  on  circular  surfaces  (which  is  given 
hereafter)  to  be  more  clearly  understood.  The  external 
and  internal  angle  mouldings  in  these  coves  may  be 
formed  with  a  jack  template  or  as  described  for  coves. 

Circle  Mouldings  on  Circular  Surfaces, — The  accom- 
panying illustration,  Plate  III,  is  given  to  elucidate 
various  methods  of  running  circular  mouldings  on  cir- 
cular surfaces,  shows  the  elevation  of  a  cove  suitable  for 
an  aquarium  or  marine  hall.  The  external  angle  rib 
moulding,  C,  and  the  panel  rib  moulding,  D,  spring  from 
the  top  or  weathering  of  a  main  moulding,  and  intersect 
with  a  horizontal  or  crown  moulding  at  the  top  of  the 
cove.    The  section  of  the  horizontal  moulding  is  shown 


METHODS  OF  WORK 


235 


at  G,  and  the  section  of  the  panel  moulding  is  shown 
above  D ;  the  section  of  the  external  rib  being  of  course 
double  that  of  the  panel  moulding.  Where  circular  or 
straight  mouldings  intersect  with  each  other,  it  is  ad- 
v^antageous  in  most  cases  to  run  the  circular  mouldings 
first,  so  that  the  whole  of  the  moulding  can  be  run, 
and  leave  the  intersection  to  be  mitred  on  the 
straight  part,  which  is  naturally  the  easiest  part.  In 
some  examples  it  is  not  advisable  to  run  the  circular  part 
first.  For  example,  if  the  crown  or  horizontal  moulding, 
as  shown  at  G,  Fig.  1,  was  the  lower  part  of  a  large 
crown  moulding  made  to  intersect  with  small  cove 
mouldings,  it  would  be  best  to  run  the  straight  moulding 
first,  and  then  cut  away  as  much  of  the  straight  mould- 
ing as  will  allow  the  nib  of  the  running  mould  to  pass 
while  running  the  circular  moulding.  For  the  section 
in  this  example  there  would  be  very  little  mitring  to  do, 
as  it  would  simply  be  a  butt  mitre  up  to  the  back  of  the 
circular  mouldings.  The  external  rib  moulding,  C,  is 
best  run  with  a  jack  template.  The  circular  panel 
mouldings  (one-half  of  a  moulding  is  shown  at  D)  can 
be  run  by  two  methods.  By  the  first,  the  moulding  is 
run  in  three  parts,  using  a  sledge-slippered  running 
mould  fixed  on  a  hinged  radius-rod,  and  the  two  straight 
parts  are  run  from  running  rules.  By  the  second 
method,  the  whole  moulding  is  run  at  one  operation  by 
using  a  fibrous  plaster  template,  made  as  already  de- 
scribed. 

Forming  Niches. — Niches  are  recesses  formed  in  walls, 
sometimes  for  the  purpose  of  placing  some  ornamental 
object  in  them,  such  as  statues,  vases,  &c.,  and  they  are 
often  constructed  in  thick  walls  in  order  to  save  mate- 
rials. The  plans  or  bases  of  niches  are  generally  semi- 
circular, but  some  partake  of  all  the  segments  under  a 


236  CEMENTS  AND  CONCRETES 


semicircle,  while  others  are  elliptical,  and  in  a  few  in- 
stances they  are  square  or  rectangular.  The  elevations 
of  niches  are  generally  in  accordance  with  their  plans, 
but  variations  from  this  Tule  are  sometimes  met  with. 
The  crown  or  heads  of  niches  are  generally  plain,  but 
they  are  sometimes  enriched  with  scalloped  shells,  &c., 
or  panelled  with  mouldings.  With  respect  to  the  pro- 
portion of  niches,  there  is  no  fixed  rule,  but  the  general 
one  is  twice  and  a  half  their  width  for  their  height. 
Various  methods  are  employed  in  the  formation  of 
niches.  The  crowns  of  circular  niches  are  generally  run 
with  a  mould,  because  being  circle  on  circle  and  small 
in  surface,  it  is  difficult  to  finish  them  true  and  smooth 
by  hand. 

The  accompanying  illustration  (No.  23)  elucidates 
two  methods  of  forming  semicircular  niches  with  the  aid 
of  running  moulds.  Fig.  1  shows  the  elevation,  and  Fig. 
2  the  section  of  the  crown  and  a  part  of  the  body  of 
niche,  with  the  centre-boards  and  moulds  in  position 
when  forming  the  crown  of  the  niche.  Fig.  4  shows  the 
section  of  the  body  of  the  cove,  with  the  mould  in  posi- 
tion when  forming  same.  By  the  first  method  the  niche 
is  formed  in  two  operations,  and  by  the  second  method 
it  is  formed  in  one  operation  only.  For  the  first  method, 
cut  a  running  mould  to  the  section  of  the  niche,  as  shown 
at  B,  Fig.  1,  then  fix  it  on  the  centre  board,  A,  with  two 
hinges,  keeping  the  upper  surface  or  mould  plate  level 
with  the  top  edge  of  the  centre  board,  as  shown  on  the 
section  of  the  niche.  Fig.  2.  This  also  shows  the  end 
section  of  the  centre-board  and  the  mould,  with  the 
mould  plate  and  a  hinge.  The  dotted  line  indicates  the 
distance  the  mould  travels.  After  this,  fix  the  com- 
bined centre-board  and  mould  on  the  wall,  taking  care 
that  the  top  edge  of  the  centre-board  is  level  and  ex- 


METHODS  OF  WOEK 


237 


Forming  Niches  with  Running  MoutDS. 

NO.  23. 


238  CEMENTS  AND  CONCRETES 

actly  at  the  springing  of  the  crown,  C.  The  face  of  the 
wall  must  be  floated  plumb,  and  an  allowance  made  by 
means  of  dots  for  the  thickness  of  the  setting  coat  be- 
fore the  centre-board  is  fixed.  After  the  crown  is  fin- 
ished, the  centre-board  and  running  mould  is  taken  off 
the  wall  and  separated.  The  mould  is  then  horsed  with 
two  slippers  to  allow  of  its  running  the  body  or  vertical 
part  of  the  niche.  The  mould  works  on  a  running  rule 
fixed  on  one  of  two  screeds  which  are  formed  on  the  face 
of  the  wall,  one  on  each  side  of  the  opening.  Care  must 
be  taken  that  the  screeds  are  plumb  with  the  centre-board 
dots.  Fig.  3  shows  an  elevation  of  the  mould  when 
horsed.  B  is  the  mould,  D  is  a  connecting  board  on 
which  the  mould  is  fixed  by  means  of  the  cleats,  C,  C, 
and  F,  F,  are  the  slippers.  Fig.  4  shows  an  end  section 
of  the  horsed  mould  in  position  when  running  the  body 
of  the  niche.    The  base  is  finished  by  hand. 

By  the  second  method  the  niche  is  run  in  one  opera- 
tion, as  already  mentioned.  This  is  effected  by  cutting 
a  running  mould  to  the  vertical  section  of  the  niche,  then 
fixing  a  pivot  at  the  bottom  and  a  bolt  at  the  top.  A 
wood  block,  with  a  socket  to  fit  the  bolt  on  the  mould,  is 
let  into  the  face  of  the  wall  at  the  top  of  the  nichC;,  and 
temporaril}^  fixed,  then  another  block  with  a  socket  to  fit 
the  pivot  of  the  mould  is  fixed  at  the  bottom  of  the 
niche.  Care  must  be  taken  that  the  sockets  are  plumb 
and  in  a  line  with  the  centre  of  the  niche,  also  that  they 
are  in  a  line  with  the  face  of  the  wall^  so  as  to  allow 
the  mould  to  form  a  true  semicircle  with  perpendicular 
arrises.  Place  the  pivot  of  the  mould  in  the  socket,  and 
push  the  bolt  up  and  secure  it,  and  the  mould  is  ready 
for  working. 

Fig.  5  shows  a  section  of  the  niche  with  the  mould  in 
position.    A  is  the  mould  with  the  pivot  and  bolt,  and 


METHODS  OF  WORK 


239 


B,  B,  are  the  socket  blocks.  A  plan  of  the  niche  and 
mould  is  shown  at  Fig.  6.  This  also  shows  the  plan  of 
the  pivot  block,  and  a  board  which  is  sometimes  used  to 
secure  the  block.  The  dotted  line  indicates  the  dis- 
tance the  mould  travels.  When  there  are  splays  or  beads 
on  the  angle  of  the  niche,  the  crown  part  is  run  with  a 
radius-rod  mould  from  a  centre-board,  and  the  vertical 
parts  with  a  ^^twin-slipper  running  mould''  on  running 
rules  fixed  on  the  wall  screeds,  or  with  a  nib  running 
mould  on  a  slipper  and  a  nib  running  rule. 

The  vertical  parts  of  the  beads  or  splays  may  also  be 
run  with  the  mould  shown  in  Fig.  3.  For  this  purpose 
two  plates  cut  to  the  desired  section  must  be  fixed  on  the 
mould,  one  at  each  side.  The  crown  part  is  run  with  a 
radius-rod,  as  already  mentioned.  The  crown  surface 
and  the  angle  moulding  can  also  be  run  in  one  operation. 
This  is  effected  by  cutting  a  mould  plate  to  the  section  of 
the  moulding,  including  the  section  of  the  crown  sur- 
face, then  horsing  it  with  a  slipper  to  run  on  the  wall 
surface,  and  a  pivot  to  fit  a  socket  formed  in  a  centre- 
board, or  with  a  radius-rod  to  work  on  a  centre-board. 
A  pivot  will  be  found  most  suitable  for  small  work  and 
a  radius-rod  for  large  work.  In  either  case  they  must 
be  fixed  on  the  centre  of  the  mould,  so  as  to  be  in  a  line 
with  the  mould  plate.  After  the  crown  is  run,  the  mould 
plate  of  the  crown  surface  is  cut  off^  and  the  remaining 
part  of  the  mould  used  for  running  the  vertical  mould- 
ings. 

In  some  designs  a  small  moulding,  such  as  an  impost 
moulding,  is  carried  round  the  body  surface  of  the  niche, 
and  in  a  line  with  the  springing  of  the  crown.  This 
moulding  can  be  run  in  a  similar  way  as  shown  at  Fig. 
5,  or  by  fixing  a  flexible  wood  or  a  plaster  running  rule 
on  the  body  of  the  niche  for  the  mould  to  run  on. 


240 


CEMENTS  AND  CONCRETES 


The  crowns  of  niches  that  are  parallel  with  small 
mouldings  are  best  executed  by  making  a  model  of  the 
design,  then  moulding  it  and  casting,  and  fixing  as  many 
as  are  required.  In  niche  crowns  that  are  enriched 
with  shells,  foliage,  &c.,  the  enrichment  should  be  cast 
with  the  crown  surface  as  a  background.  Fibrous  plas- 
ter is  well  adapted  for  the  construction  of  niches.  For 
this  purpose  a  reverse  casting  mould  should  be  employed 
for  forming  the  casts.  This  is  made  by  cutting  a  re- 
verse running  moidd  to  the  section  of  the  niche,  and  after 
a  sufficient  length  of  the  body  is  run,  cut  the  mould  in 
half  and  run  the  crown.  Then  fix  it  on  the  end  of  the 
run  body,  and  then  fix  rules  at  the  sides  and  ends  to 
form  fences  and  rims,  thus  completing  the  casting 
mould. 

Any  of  the  above  methods  for  forming  niches  with 
running  moulds  can  be  advantageously  used  for  forming 
the  body  and  crown  of  the  Ionic  niche  when  such  is  re- 
quired. 

EuNNiNG  AN  Elliptical  Moulding  in  Situ. 

In  No.  24  a  method  of  running  an  elliptical  curve  with 
a  trammel  is  shown.  Fig.  1  represents  the  front  eleva- 
tion of  the  trammel  mounted  and  in  working  order,  and 
Fig.  2  is  a  section  of  the  same. 

Take  two  floor  boards,  B,  long  enough  to  reach  to  the 
springing  line  of  the  arch,  and  nail  them  on  the  back  of 
two  lengths  of  5  in.  by  2  in..  A,  which,  as  shown  may  be 
somewhat  longer.  Fix  these  up  inside  the  jambs  of  the 
opening,  taking  care  to  see  that  they  are  perfectly  up- 
right, and  keep  them  the  thickness  of  the  trammel  boards 
(which  is  1  in.)  back  from  the  face  of  the  opening  on 
which  the  architrave  is  to  be.    Then  cut  three  pieces  of 


METHODS  OF  WORK 


241 


5  in.  by  2  in.,  C,  tight  in  between  and  secure  them  in 
place  with  3  in.  cut  nails,  taking  care  to  see  that  the 
bottom  side  of  the  top  one  is  above  the  springing  line. 
Then  prepare  the  trammel  boards,  D  and  E,  6  in.  by  1 


PLASTEEERS  TRAMMEL  £0R  ELLIFTIGAL  ARCHITRAVE.' 


NO.  24. 

in.,  and  cut  the  slots,  which  are  %  in.  wide  and  of  a 
length  which  may  be  easily  ascertained  by  simple  geom- 
etry.   Halve  the  boards  together  at  the  joint  and  fur- 
ther secure  them  by  screwing  a  plate  of  the  thickest  sheet 
zinc  obtainable  on  the  back,  as  per  Fig.  3.   Nail  the 


242  CEMENTS  AND  CONCRETES 


boards  up  as  shown,  keeping  the  horizontal  slot  central 
on  the  springing  line  and  the  vertical  slot  exactly  in  the 
centre  of  the  opening,  and  be  most  particular  to  see  that 
the  whole  lot  is  perfectly  upright  and  level.  Next  pre- 
pare the  trammel  stick,  2  in.  by  1  in.,  and  mount  the 
mould  on  the  top  in  the  usual  manner,  as  shown.  Then 
insert  the  pins  in  holes  bored  in  the  stick  and  secure  by 
a  screw  through  the  edge.  Have  them  just  thick  enough 
to  work  comfortably  in  the  slots,  and  keep  the  centre  of 
the  pin  XI,  the  distance  of  the  rise,  and  the  centre  of 
the  pin  X2,  the  distance  of  the  half  sp^n  from  the  bot- 
tom member  of  the  architrave.  All  the  timber  may  be 
deal  except  the  pins,  which  must  be  of  some  kind  of  hard 
wood.  If  well  made  and  used  with  care  this  trammel 
ought  to  serve  many  times ;  the  pins,  of  course,  needing 
adjustment  for  arches  of  different  size. 


MISCELLANEOUS  MATTERS. 


Depeter, — This  is  a  sort  of  a  rough-cast,  and  consists 
of  forming  a  fair  surface  with  coarse  stuff  or  Portland 
cement.  As  soon  as  laid  a  hand-fiaat  is  parred  over  the 
surface  a  few  times  to  give  it  an  even  and  uniform  tex- 
ture, and  while  it  is  soft,  pressing  in  by  hand,  small 
pieces  of  hard  coal,  broken  bottles^  pottery,  bricks,  shells, 
stones,  pebbles,  or  marble.  The  design  may  be  varied  and 
enriched  by  using  various  colored  pieces  in  forming  mar- 
gins, bands  or  other  ornamentation.  On  the  contrast  of 
colors  and  the  broad  bands  depends  the  effect  of  this 
class  of  work.  A  combination  of  ^'Depeter"  and  rough- 
cast may  be  used  with  excellent  effect. 

Sgraffitto. — Sgraffitto  or  ^^graffitto''  is  an  Italian  word, 
and  means  scratched."  Scratched  decoration  is  the 
most  ancient  mode  of  surface  decoration  employed  by 
man.  The  primitive  savage  of  the  flint-weapon  period 
used  this  simple  form  of  ornamentation.  Scratched 
work,  a;s  used  by  prehistoric  man,  may  be  fitly  termed 
the  proem  of  the  civilized  arts  of  drawing,  modelling  and 
sculpture.  The  term  is  now  employed  for  plaster  deco- 
rations, scratched  or  incised  upon  plaster  or  cement  be- 
fore it  is  set.  It  may  be  used  for  both  external  and 
internal  decoration.  The  annexed  illustrations  (Nos.  25 
and  26)  will  demonstrate  the  high  degree  to  which  the 
art  of  sgraffitto  attained  in  Italy. 

Some  graffittos  are  really  low  relief  work  rather  than 
the  sgraffitto,  they  being  very  deep  cut  with  the  iron  or 
steel  point,  which  was  necessitated  by  the  final  coat  be- 
ing plastered  on  instead  of  washed  on.    Deep  cutting 

243 


MISCELLANEOUS  MATTERS  245 


gives  a  hard  appearance  to  the  design,  prevents  the  water 
from  running  off  the  walls,  and  catches  the  dirt.  In  exe- 
cuting true  sgraffitto,  the  cut  or  scratch  should  be  ex- 
ceedingly slight — in  fact,  some  parts  scarcely  percepti- 
ble. 

Sgraffitto  decorations  do  not  suffer  materially  from 
stubbing  it  with  an  old  broom,  leaving  it  barely  half  an 
inch  from  the  finished  face.  For  internal  work,  the  ordi- 
nary pricking  up  suffices.  When  this  is  dry,  a  thin  coat 
of  selentic  lime  mixed  with  the  desired  coloring  matter 
for  the  background,  is  floated  over  it.  This  background 
may  be  black,  bone-black  being  used ;  red,  for  which  use 
Venetian  or  Indian  red,  or  the  ordinary  purole  brown 
of  commerce,  singly  or  mixed,  to  produce  any  tone  de- 
sired; yellow,  produced  by  ochres  or  umbers;  blue,  by 
German  blue,  Antwerp  blue,  or  any  of  the  commoner 
blues,  avoiding  cobalt,  and  these  colors  you  may  use  to 
any  degree  of  intensity  or  paleness.  When  this  coat  is 
nearly  dry,  skim  over  it  a  very  thin  coat  of  pure  selentic 
lime,  which  dries  of  a  parchment  color  and  generally 
suffices.  If  you  want  a  pure  white  lime,  use  a  moderate 
quick-setting  one,  as  stiff  as  you  can  work  it,  and  as 
each  variety  of  lime  has  its  own  individual  perversity,  I 
can  give  no  general  direction,  and  would  advise  the  be- 
ginner to  stick  to  selentic,  which  is  always,  procurable. 
You  have,  of  course,  prepared  your  cartoon.  This  is 
pricked  and  pounced  as  for  any  other  transfer  process, 
and  then  with  an  old,  well-worn,  big-bladed  knife,  for 
there  is  no  better  tool,  you  can  cut  round  all  the  out- 
lines, and  with  a  flat  spatula  clear  away  all  the  thin 
upper  coat,  leaving  the  colored  ground  as  smooth  as  you 
can.  If  your  plaster  is  not  quite  dry  enough  for  the 
two  coats  to  separate  easily,  wait  a  little  longer,  but  not 
too  long,  for  that  is  fatal.    By  the  time  you  have  cleared 


246  CEMENTS  AND  CONCRETES 


out  your  background,  the  plaster  will  be  in  a  good  con^^ 
dition  to  allow  you  to  cut  out  the  finer  parts  of  the  de- 
sign, such  as  folds  of  the  draperies,  or  the  finer  lines  of 
the  faces  or  of  the  ornament.  Use  your  knife  slightly 
on  the  slope,  and  if  you  want  to  produce  half-tones,  slope 
it  very  much;  but,  as  a  rule,  the  more  you  avoid  half- 
tones, and  the  simpler  and  purer  your  line,  the  more 
effective  your  work  will  be.  Recollect,  above  all  things, 
you  are  making  a  design  and  not  a  picture,  and  you 
must  never  hesitate,  for  to  retouch  is  impossible.  Some- 
times it  may  be  desirable  to  gild  the  background,  and 
you  can  then  carve  or  impress  it  with  any  design  you 
choose.  It  occasionally  happens  you  want  to  give  some 
semblance  of  pictorial  character  to  your  work  when  it  is 
small  in  scale  and  near  the  eye,  and  then  you  can  pro- 
ceed as  though  you  were  cutting  a  wood-block. 

By  cutting  out  your  ground  color  in  places,  and 
plastering  it  with  that  of  another  color,  you  may  vary 
any  portion  of  it  you  desire:  You  can  also  wash  over 
certain  parts  of  your  upper  coat  with  a  water-color  if 
you  desire,  combining  fresco  with  the  sgraffitto,  both  of 
which  manners  are  often  used ;  but,  as  a  rule,  the  broader 
your  design,  and  the  simpler  your  treatment  of  it,  the 
better.  It  will  be  seen  that  this  process  is  very  available 
for  simple  architectonic  effects;  and  for  churches,  hos- 
pitals, and  other  places  where  large  surfaces  have  to  be 
covered,  it  is  the  least  costly  process  that  can  be  adopted. 
It  has  also  the  great  advantage  of  being  non-absorbent, 
and  it  can  be  washed  down  at  any  time.  The  artist  is 
untrammelled  by  difficulties  of  execution,  but  he  should 
bear  in  mind  that  the  more  carefully  he  draws  his  lines 
and  the  simpler  he  keeps  his  composition,  the  more 
charmed  with  the  process  he  will  be,  and  the  better  will 
be  the  effect  of  his  work. 


MISCELLANEOUS  MATTERS  247 


A  well-known  artist  records  his  experience  of  sgraffitto 
as  follows: 

'^Rake  and  sweep  out  the  mortar  joints,  then  give  the 
wall  as  much  water  as  it  will  drink,  or  it  will  absorb 
the  moisture  from  the  coarse  coat,  as  it  will  not  set,  but 
merely  dry,  in  which  case  it  will  be'  worth  little  more 
than  dry  mud.  Care  should  be  taken  that  the  cement 
and  sand  which  compose  the  coarse  coat  should  be  prop- 
erly gauged,  or  there  may  be  an  unequal  suction  for  the 
finishing  coats.  The  surface  of  the  coarse  should  be 
well  roughened  to  give  a  good  key,  and  it  should  stand 
some  days  to  thoroughly  set  before  laying  the  finishing 
coat.  When  sufficiently  set,  fix  your  cartoon  in  its  des- 
tined position  with  nails;  pounce  through  the  pricked 
outline;  remove  the  cartoon;  replace  the  nails  in  the 
register  holes;  mark  with  chalk  spaces  for  the  different 
colors,  as  indicated  by  the  pounce  impression  on  the 
coarse  coat;  lay  the  several  colors  of  the  color  coat  ac- 
cording to  the  design  as  shown  by  the  chalk  outlines; 
take  care  that  in  doing  so  the  register  nails  are  not  dis- 
placed ;  roughen  the  face  in  order  to  make  a  good  key  for 
the  final  coat.  When  set,  follow  on  with  the  final  sur- 
face coat,  only  laying  as  much  as  can  be  cut  and  cleaned 
up  in  a  day.  When  this  is  sufficiently  steady,  fix  up  the 
cartoon  in  its  registered  position;  pounce  through  the 
pricked  outline ;  remove  the  cartoon,  and  cut  out  the  de- 
sign in  the  surface  coat  before  it  sets;  then  if  the  regis- 
ter is  correct,  cut  through  to  different  colors,  according 
to  the  design,  and  in  the  course  of  a  few  days  the  work 
should  set  as  hard  and  as  homogeneous  as  stone,  and  as 
damp-proof  as  the  nature  of  things  permit. 

*  ^  When  cleaning  up  the  ground  of  color  which  may  be 
exposed,  care  should  be  taken  to  obtain  a  similar  quan- 
tity of  surface  all  through  the  work,  so  as  to  get  a  broad 


248  CEMENTS  AND  CONCRETES 


effect  of  deliberate  and  calculated  contrast  between  the 
trowelled  surface  of  the  final  coat  and  the  scraped  sur- 
face of  the  simple'  contrasts  of  light  against  dark,  or 
dark  against  light.  The  following  are  the  proportions 
of  the  various  coats : 

' '  Coarse  coats :  One  of  Portland  cement  to  3  of  washed 
sharp  coarse  sand. 

' '  Color  ccat :  One  and  one-half  of  air-slaked  Port- 
land to  1  of  color  laid  %  inch  thick.  Distemper  colors 
are  Indian  red,  Turkey  red,  ochre,  umber,  lime  blue; 
lime  blue  and  ochre  for  green;  oxide  of  manganese  for 
black.  In  using  lime  blue,  its  violet  hue  may  be  over- 
come by  adding  a  little  ochre.  It  should  be  noted  that 
it  sets  much  quicker  and  harder  than  the  other  colors 
named. 

Final  coat,  internal  work:  Parian,  air-slaked  for 
twenty-four  hours  to  retard  its  setting,  or  fine  lime  and 
selenitic  sifted  through  a  fine  sieve. 

''For  external  work:  Three  selenitic  and  2  silver 
sand. 

''When  finishing,  space  out  the  wall  according  to  the 
scheme  of  decoration,  and  decide  where  to  begin,  and 
give  the  wall  in  such  place  as  much  water  as  it  will 
drink;  then  lay  the  color  coat,  and  leave  sufficient  key 
for  the  final  coat.  Calculate  how  much  surface  of  color 
coat  it  may  be  advisable  to  get  on  to  the  wall,  as  it  is  bet- 
ter to  maintain  throughout  the  work  the  same  duration 
of  time  between  the  laying  of  the  color  coat  and  the  fol- 
lowing on  with  the  final  surface  coat;  for  this  reason, 
that  if  the  color  sets  hard  before  laying  the  final  coat,  it 
is  impossible  to  get  up  the  color  to  its  full  strength  wher- 
ever it  may  be  revealed  in  the  scratching  of  the  decora- 
tion. When  the  color  coat  is  quite  firm,  and  all  shine 
has  passed  away  from  its  surface,  follow  on  with  the 


MISCELLANEOUS  MATTERS  249 


final  coat,  but  only  lay  as  much  as  can  be  finished  in  one 
day.  The  final  coat  is  trowelled  up,  and  the  design 
is  incised  or  scratched  out.  Individual  taste  and  experi- 
ence must  decide  as  to  thickness  of  final  coat,  but  if  laid 
between  %  inch  and  1-12  inch,  and  the  lines  cut  with 
slanting  edges,  a  side  light  gives  emphasis  to  the  fin- 
ished result,  making  the  outlines  tell  alternately  as  they 
take  the  light  or  cast  a  shadow." 

Another  methcd  which  I  have  used  in  sgraffitto  for 
external  decoration  was  done  entirely  with  Portland 
cement.  This  material  for  strap-work  or  broad  foliage, 
or  where  minuteness  of  detail  is  unnecessary,  will  be 
found  suitable  for  many  places  and  positions.  Three 
colors  may  be  used  if  required,  such  as  black  for  the 
background,  red  for  the  middle  coat,  and  grey  or  white 
for  the  final  coat.  These  colors  may  be  varied  and  sub- 
stituted for  each  other  as  desired,  or  as  the  design  dic- 
tates. The  Portland  cement  for  floating  can  be  made 
black  by  using  black  smithy  ashes  as  an  aggregate,  and 
by  gauging  with  black  manganese  if  for  a  thin  coat.  The 
red  is  obtained  by  adding  from  5  to  10  per  cent,  of  red 
oxide,  the  white  by  gauging  the  cement  with  white  mar- 
ble dust,  or  with  whiting  or  lime,  the  grey  being  the  nat- 
ural color  of  the  cement.  After  the  first  coat  is  laid, 
it  is  keyed  with  a  coarse  broom.  The  second  coat  is  laid 
fair  and  left  moderately  rough  with  a  hand-float.  The 
suction  of  the  first  coat  will  give  sufficient  firmness  to 
allow  the  third  coat  to  be  laid  on  without  disturbing  the 
second.  The  third  coat  should  be  laid  before  the  sec- 
ond is  set  hard.  The  second  and  third  coats  may  be 
used  neat,  or  gauged  with  fine  sifted  aggregate  as  re- 
quired. The  finer  the  stuff,  the  easier  and  cleaner  the 
work,  and  the  cut  lines  are  more  accurate  and  free  from 
jagged  edges.    The  outlines  of  the   design  may  be 


250  CEMENTS  AND  CONCRETES 

pounced  or  otherwise  transferred  to  the  surface  of  the 
work,  and  the  details  put  in  by  hand.  The  thickness  of 
the  second  coat  should  be  about  3-16  inch,  and  the  third 
coat  about  %  inch.  The  thickness  of  one  or  both  coats 
may  be  varied  to  suit  the  design.  The  beauty  of  effect 
of  this  method  of  linear  decoration,  aided  by  two  or 
three  colors,  depends  greatly  on  the  treatment  of  design, 
the  clearness  of  the  incised  lines,  and  the  pleasing  color 
contrasts.  It  will  be  seen  that  in  the  three  methods 
described  there  is  a  similarity,  yet  the  method  of  using 
two  color  coats  on  a  dark  floating  coat  will  give  more 
variety  and  effect.  There  is  a  large  use  for  sgraffitto  in 
the  future,  as  it  has  been  in  the  past,  and  its  use  is  inti- 
mately bound  up  with  the  future  of  cement  concrete. 

In  order  that  the  foregoing  examples  of  high-class 
sgraffitto  may  not  deter  the  young  plasterer  from  trying 
his  ' '  'prentice  han '  "  in  this  class  of  work,  some  simple 
designs  are  given  in  the  annexed  illustration  (No.  27). 
Fig.  1  shows  a  design  for  a  frieze  in  two  colors.  The 
ground  may  be  black  or  red,  and  the  ornament  buff  or 
grey.  The  colored  material  for  the  ornament  is  laid 
first,  and  the  colored  material  for  the  ground  laid  last. 
Pig.  2  shows  a  design  for  a  cove  in  two  colors,  one  with 
two  shades.  The  ground  is  grey,  and  the  band  work 
buff.  A  deeper  shade  of  buff  for  the  honeysuckle  can  be 
obtained  by  brushing  this  part  with  liquid  color  made 
deeper  than  the  original  gauge,  also  by  laying  a  black 
coat  first,  and  in  a  line  with  the  honeysuckle ;  then  laying 
the  buff  stuff  for  the  band  work  next,  and  then  laying 
the  grey  color  last.  In  the  latter  case  the  honeysuckle 
is  cut  deeper  than  the  band  work,  so  as  to  expose  the 
black  coat. 

Different  effects  can  be  obtained  by  changing  the  col- 


MISCELLANEOUS  MATTERS  251 


ors.  Sections  of  the  surface  of  the  frieze  and  part  of  the 
moulding  are  shown  at  the  ends. 

Fresco, — The  plasterer  is  closely  allied  to  the  artist 
painter.  He  has  always  to  be  in  readiness  to  plaster  the 
wall  for  the  artist.  Owing  to  the  alliance  with  distin- 
guished artists,  and  the  various  methods  of  preparing 
and  using  the  plaster  materials,  I  am  induced  to  give  a 
few  notes,  also  extracts  from  writers  of  authority. 


-Sgraffitto  Frieze  in  Two  Cx^lours. 
NO.  27. 


Fresco  is  a  mode  of  painting  with  water-colors  on  freshly 
laid  plaster  while  it  remains  naturally  wet.  It  is  called 
''fresco"  either  because  it  was  originally  used  on  build- 
ings in  the  open  air,  or  because  it  was  done  on  fresh 
plaster.    Fresco  is  an  ancient  art,  being  mentioned  by 


252  CEMENTS  AND  CONCRETES 


Pliny.  Mr.  Flinders  Petrie  found  some  remarkably  fine 
specimens  on  floors  and  walls  at  Tel-el- Amarna,  which 
reveal  the  state  of  the  art  four  thousand  years  ago.  Fine 
frescoes  were  discovered  in  the  ruins  of  Pompeii.  In 
one  of  the  principal  houses  the  plaster  walls  are  adorned 
with  theatrical  scenes;  in  an  inner  room  is  the  niche 
often  to  be  seen  in  Pompeiian  houses.  The  frescoes  on 
the  wall  consist  of  floral  dados.  Above  this  is  a  whole 
aquarium,  with  shells,  plants,  birds  and  animals.  They 
are,  all  executed  in  their  natural  colors,  and  are  natur- 
ally and  gracefully  drawTi.  Michael  Angelo's  beautiful 
fresco  on  the  ceiling  of  the  Sistine  Chapel  in  the  Vatican 
is  grand  both  in  conception  and  execution.  It  measures 
133  feet  in  length  by  43  feet  in  width.  Eaphael's  fres- 
coes in  the  Vatican,  Farnesina  Palace,  &c.,  are  wonder- 
fully fine,  and  may  be  regarded  as  the  high-water  mark 
of  Cinque  Cento  decoration. 

For  fresco  or  buon  fresco  the  lime  has  to  be  care- 
fully run,  and  the  sand  should  be  white,  clean,  and  of 
even  grain,  being  well  washed  and  sifted  to  free  it  from 
impurities  or  saline  properties.  Silver  sand  is  pre- 
ferred by  some  artists.  The  older  the  putty  lime,  the 
better  the  results.  The  lime  is  slaked  in  a  tub,  and  then 
run  through  a  fine  wire  sieve  into  a  tank,  and  after  being 
covered  up,  is  left  for  three  months.  It  is  then  put  into 
the  tub  again,  and  re-slaked,  or  rather  well  worked,  and 
run  through  a  fine  hair  sieve  into  earthenware  jars  or 
slate  tanks,  and  the  water  which  collects  at  the  top  drawn 
or  poured  off,  the  jars  or  tank  being  covered  over  to  ex- 
clude the  air.  Lime  putty  in  this  state  will  keep  for  an 
indefinite  time  without  injury.  From  2  to  4  parts  of 
sand  to  1  part  putty  is  usual.  Marble  dust  alone  is 
sometimes  used  in  place  of  sand,  and  also  sand  with 
equal  parts.    Every  difference  of  lime  and  sand  found 


MISCELLANEOUS  MATTERS  253 

in  various  localities  should  be  considered  and  tested  be- 
fore using.  A  soft  sand  is  quickly  dissolved  by  a 
strong  lime,  and  a  plaster  made  of  this  is  fit  for  use 
sooner,  and  will  deteriorate  more  quickly  than  a  plaster 
made  with  a  less  powerful  lime  and  a  harder  sand,  or 
with  marble  dust. 

The  wall  surface  to  be  plastered  must  be  well  scraped 
and  hacked,  the  joints  raked  out  and  brushed,  and  the 
whole  surface  well  scrubbed  and  wetted.  The  rendering 
is  done  with  the  best  possible  prepared  old  coarse  stuff. 
If  the  walls  are  rough  or  uneven,  they  should  be  first 
pricked  up  and  then  floated.  In  any  case,  the  surface 
is  left  true,  and  with  a  rough  face,  to  receive  the  fin- 
ishing coat.  Portland  cement  or  hydraulic  lime  gauged 
with  sand,  also  gauged  with  coarse  stuff,  has  been  used 
where  the  walls  were  damp  (damp  is  fatal  to  fresco), 
or  if  exposed  to  the  atmosphere.  When  Portland  cement 
or  hydraulic  lime  is  used,  the  work  should  be  allowed  to 
stand  until  thoroughly  dry  to  allow  any  contained  sol- 
uble saline  efflorescence  to  come  to  the  surface.  This  is 
brushed  off  with  a  dry  brush,  and  a  few  days  are  allowed 
to  elapse  to  see  if  there  is  a  further  efflorescence.  When 
this  is  all  extracted  and  swept  off,  and  the  artist  is  ready 
to  commence,  the  wall  is  washed  with  a  thin  solution  of 
the  fine  setting  stuff,  and  then  laid  about  %  inch  thick, 
with  well-beaten,  worked,  and  tempered  fine  setting 
stuff.  It  is  then  rubbed  with  a  straight-edge  and  scoured 
with  a  hand-float  (using  lime  water  for  scouring)  until 
the  surfacei  is  true  and  of  uniform  grain.  Most  artists 
prefer  a  scoured  surface  without  being  trowelled.  No 
more  surface  should  be  covered  than  can  be  conven- 
iently painted  in  one  day.  While  the  plaster  is  still 
soft  and  damp,  the  cartoon  iis  laid  on,  and  the  lines  and 
details  pounced  in  or  indented  by  means  of  a  bone  or 


254  CEMENTS  AND  CONCRETES 


hard-wood  tool.  Should  the  finishing  coat  get  too  dry 
in  any  part,  it  can  be  made  fit  for  work  by  using  a  fine 
spray  of  water.  The  method  of  plastering  and  the  gaug- 
ing of  materials  may  slightly  vary  according  to  the  de- 
sire of  the  painter  and  the  kind  of  fresco  in  hand.  The 
following  is  taken  from  an  old  manuscript  dated  1699  : — • 

'^1.  In  painting  the  wall  to  make  it  endure  the 
weather,  you  must  grind  colors  with  lime  water,  milk,  or 
whey,  mixed  in  size. 

''2.  Then  paste  or  plaster  must  be  made  or  well- 
washed  lime,  mixed  with  powder  of  old  rubbish  stones. 
The  lime  must  be  often  washed  till  finally  all  the  salt  is 
extracted,  and  all  your  work  must  be  done  in  clear  and 
dry  weather. 

'^3.  To  make  the  work  endure,  stick  into  the  wall 
stumps  of  headed  nails,  about  5  or  6  inches  asunder,  and 
by  this  means  you  may  preserve  the  plaster  from  peeling. 

"4:.  Then  with  the  paste  plaster  the  walls  a  pretty 
thickness,  letting  it  dry;  but  scratch  the  first  coat  with 
the  point  of  your  trowel  longways  and  crossways,  as 
soon  as  you  have  done  laying  on  what  plaster  or  paste 
you  think  fit,  that  the  next  plastering  you  lay  upon  it 
may  take  good  key,  and  not  come  off  nor  part  from  the 
first  coat  of  plastering;  and  when  the  first  coat  is  dry, 
plaster  it  over  again  with  the  thickness  of  half  a  barley- 
corn, very  fine  and  smooth.  Then,  your  colors  being  al- 
ready prepared,  work  this  last  plastering  over  with  the 
said  colors  in  what  draught  or  design  you  please — his- 
tory, etc.,t — so  will  your  painting  unite  and  join  fast  to 
the  plaster,  and  dry  together  as  a  perfect  compost. 

'^Note — ^Your  first  coat  of  plaster  or  paste  must  be 
very  haired  with  ox-hair  in  it,  or  else  your  work  will 
crack  quite  through  the  second  coat  of  plastering;  and 
will  spoil  all  your  painting  that  you  paint  upon  the  sec- 


MISCELLANEOUS  MATTERS  255 


end  coat  of  plastering;  but  in  the  second  coat  that  is 
laid  on  of  paste  or  plaster  there  must  be  no  hair  in  it  at 
all,  but  made  thus: — 

Mix  or  temper  up  with  well-washed  lime,  fine  powder 
of  old  stones  (called  finishing  stuff)  and  sharp  grit  sand, 
as  much  as  you  shall  have  occasion  for,  to  plaster  over 
your  first  coat,  and  plaster  it  all  very  smooth  and  even, 
that  no  roughness,  hills,  nor  dales,  be  seen,  nor  scratch  of 
your  trowel.  The  best  way  is  to  float  the  second  coat  of 
plastering  thus: — After  you  have  laid  it  all  over  the 
first  coat  with  your  trowel  as  even  and  smooth  as  pos- 
sible, you  can  then  take  a  float  made  of  wood,  ver^^ 
smooth,  and  1  foot  long  and  7  or  8  inches  wide,  with  a 
handle  on  the  upper  side  of  it  to  put  your  hand  into 
to  float  your  work  withal,  and  thus  will  make  your 
plastering  to  lie  even;  and  lastly,  with  your  trowel  you 
may  make  the  said  plastering  as  smooth  as  possible. 

''5.  In  painting  be  nimble  and  free;  let  your  work 
be  bold  and  strong;  but  be  sure  to  be  exact,  for  there  is 
no  alteration  after  the  first  painting,  and  therefore 
heighten  your  paint  enough  at  first;  you  may  deepen  at 
pleasure. 

^^6.  All  earthy  colors  are  best,  as  the  ochres,  Spanish 
brown,  terra-vert,  and  the  like.  Mineral  colors  are 
naught. 

^'7.  Lastly,  let  your  pencil  and  brushes  be  long  and 
soft,  otherwise  your  work  will  not  be  smooth;  let  your 
colors  be  full,  and  flow  freely  from  the  pencil  or  brush; 
and  let  your  design  be  perfect  at  first,  for  in  this  there 
is  no  alteration  to  be  made." 

Fresco  Secco. — Closely  allied  with  the  genuine  fresco 
(fresco  buono)  is  another  kind  called  fresco  secco  (dry), 
or  mezzo  (half)  fresco.  The  plaster  work  for  fresco  sec- 
co is  similar  to  that  used  for  fresco  buono.    It  is  allowed 


256  CEMENTS  AND  CONCRETES 


to  stand  until  thoroughly  dry.  The  surface  is  then 
rubbed  with  pumice-stone,  and  about  twelve  hours  before 
the  painting  is  commenced  it  is  thoroughly  wetted  with 
water  mixed  with  a  little  lime.  The  surface  is  again 
moistened  the  next  morning,  and  the  painting  begun  in 
the  usual  way.  If  the  wall  should  become  too  dry,  it  is 
moistened  with  the  aid  of  a  syringe.  There  is  no  fear  of 
joinings  in  the  painting  being  observable,  and  the  artist 
can  quit  or  resume  his  work  at  pleasure.  Joinings  are 
distinctly  noticeable  in  the  frescos  in  the  Loggia  of  the 
Vatican.  Fresco  secco  paintings  are  heavy  and  opaque, 
whereas  real  fresco  is  light  and  transparent.  While  the 
superiority  of  fresco  buono  over  fresco  secco  for  the 
hi.ghest  clasis  of  decorative  painting  is  unquestionable, 
still  the  latter  is  suitable  for  many  places  and  forms  of 
decorative  paintings.  The  head  by  Giotto  in  the  National 
Gallery,  from  the  Brancacci  Chapel  of  the  Carmine  at 
Florence,  is  in  fresco  secco. 

Indian  Fresco  and  Marble  Plaster, — ^ 'Fresco  painting 
is  a  common  mode  of  decoration  in  Jeypore,  and  is  used 
in  ornamenting  walls  inside  and  outside  of  buildings — 
also  as  a  dado  or  border  round  the  wainscot  or  on  the 
floor — and  on  any  surface  where  decoration  is  desired. 
The  beautiful  marble  planter  on  which  it  is  done  is  com- 
mon Rajputana,  and  is  used  to  line  the  surface  of  walls 
or  floors,  and  of  baths  or  bath-rooms.  It  is  admirably 
adapted  to  places  where  coolness  and  cleanliness  are  de- 
sired, and  is  very  suitable  to  a  warm  climate.  It  would 
no  doubt  be  more  commonly  used  if  pure  lime  could  be 
obtained. 

' '  To  prepare  the  marble  plaster,  the  process  in  use  in 
Jeypore  is  as  follows: — Take  pure  stone  lime,  mix 
it  with  water  until  it  has  dissolved,  then  strain  it  through 
a  fine  cloth.    In  Jeypore  the  lime  is  made  from  pounded 


MISCELLANEOUS  MATTERS  257 


marble  chips  or  almost  pure  limestone.  The  substance 
which  remains  in  the  cloth  is  called  bujra,  and  all  that 
passes  through  the  cloth  is  called  ghole.  These  should 
be  prepared  a  few  days  before  they  are  required  so  as 
to  allow  time  to  settle,  and  every  day  the  water  should 
be  changed,  so  as  to  leave  a  very  fine  sediment. 

^^Jinki,  which  is  also  used,  is  pure  marble  ground  to 
a  very  fine  powder;  kurra  is  a  mixture  of  bujra  and 
jinki;  and  jinkera  is  a  mixture  of  ghole  and  kurra. 
These  are  the  materials  used,  and  the  names  by  which 
they  are  known  in  Jeypore.  In  Madras,  where  similar 
plaster  is  used,  it  is  made,  I  believe,  from  shells  and  the 
ingredients  are  probably  known  by  other  local  names. 

^^If  tlie  surface  to  be  polished  is  a  slab  or  stone^  the 
kurra  mixture  consists  of  1  part  by  weight  of  burja  and 
1%  parts  of  jinki.  If  the  surface  is  a  wall  or  a  chunam 
floor,  it  must  be  first  thoroughly  dry  and  consolidated- 
then  take  equal  parts  of  burja  and  jinki  to  form  the 
kurra  mixture.  Mix  the  burja  and  the  jinki  well  to- 
gether; add  a  little  water  and  grind  them  well  together, 
in  the  same  ways  as  natives  mix  their  condiments,  by 
hand  with  a  stone  rolling-pin  on  a  slab,  until  they  form 
a  perfectly  fine  paste.  Wet  the  surface  which  is  to  be 
polished,  and  spread  over  it  a  layer  of  this  kurra  mix- 
ture, about  %  inch  thick.  Then  beat  the  surface  gently 
with  a  flat  wooden  beater,  sprinkling  a  few  drops  of 
clean  water  on  the  surface  occasionally.  Then  mix  a 
little  ghole  with  the  kurra  plaster  (described  above  as 
jinkera)  and  lay  it  on  evenly  with  a  brush  as  if  it  were 
a  coat  of  paint ;  rub  the  surface  over  carefully  with  any 
clo'se-grained  flat  stone,  called  in  Jeypore  jhaon.  The  ob- 
ject of  this  is  to  smooth  down  all  irregularity  and 
roughness,  and  to  prepare  a  smooth  even  surface. 
Sprinkle  a  few  drops  of  water  and  repeat  the  process, 


258  CEMENTS  AND  CONCRETES 


taking  care  that  no  hollow  places  are  allowed  to  re- 
main. Paint  it  over  with  fine  jinkera  (ghole  and 
kurra  mixed),  increasing  the  proportion  of  ghole,  and 
rub  it  down  well  with  a  flat  stone  (jhaon)  as  before; 
then  paint  it  over  with  ghole  only,  after  each  coat  rub- 
bing it  down  carefully  with  the  jhaon  stone.  After  this, 
rub  it  all  over  with  a  soft  linen  cloth,  called  in  Jeypore 
nainsukh,  folded  into  a  pad.  Then  give  it  another  coat 
of  ghole,  and  now  rub  it  down  carefully  with  a  piece  of 
polished  agate,  called  in  Jeypore  ghinti,  until  it  begins 
to  shine.  The  surface  must  not  be  allowed  to  dry  too 
rapidly,  or  a  good  polish  will  not  be  obtained.  Care 
must  be  taken  that  the  lime  has  been  thoroughly  slaked 
in  the  first  instance,  or  it  may  blister;  also  that  the  sur- 
face, if  a  floor,  is  thoroughly  consolidated^  as  the  least 
settlement  naturally  causes  the  plaster  to  crack.  The 
polishing  process  with  the  agate  cannot  be  repeated  too 
often;  the  more  it  is  carefully  done,  the  better  will  be 
the  polish.  Every  time  the  agate  is  moved  backwards 
it  should  be  made  to  pass  over  a  portion  of  its  previous 
course,  so  as  to  prevent  any  mark  or  line  at  the  edge. 
Lastly,  if  the  surface  is  to  remain  white,  take  some  water 
which  has  been  mixed  with  grated  cocoanut,  and  lay  it 
on  the  surface.  Let  it  dry,  and  then  rub  it  down  with  a 
fine  cloth  folded  into  a  pad.  If  any  coloring  is  desired, 
the  same  process  is  adopted  until  the  polishing  with  the 
agate  is  begun.  This  is  only  done  slightly.  If  any  pat- 
tern is  desired,  it  is  drawn  on  paper  and  pricked  out. 
The  paper  is  placed  on  the  surface,  and  is  dusted  with 
very  finely  powdered  charcoal  tied  up  in  a  muslin  bag. 
The  charcoal  passes  through  the  perforations  and  marks 
the  plaster  surface.  The  paints  are  mixed  with  water, 
and  are  painted  on  by  h^nd  while  the  surface  is  still 
fresh  and  moist  hence  the  term  fresco.    Where  a  large 


MISCELLANEOUS  MATTERS  259 


surface  has  to  be  done,  it  is  necessary  to  employ  several 
men  at  the  same  time,  in  order  that  the  surface  might 
be  all  painted  before  it  has  time  to  dry ;  or  else  the  pat- 
tern must  be  so  arranged  that  the  connection  of  one 
day^s  work  with  the  work  of  the  next  will  not  be  amiss. 
Immediately  after  the  surface  has  been  painted  the 
colors  are  beaten  in  with  the  back  of  a  small  trowel,  in 
such  a  manner  that  the  color  is  not  rubbed  or  mixed 
with  the  color  adjacent.  As  soon  as  it  shows  to  the 
touch  that  the  color  has  become  incorporated  with  the 
plaster,  the  surface  is  painted  over  with  water  mixed 
with  grated  cocoanut,  and  is  then  polished  down  with 
the  agate. 

^^The  following  colors  can  be  used  in  process: — Lamp 
black;  red  lead;  green  (from  a  stone  known  as  hara 
pathar)  ;  yellow  (from  a  stone  called  pila  pathar)  ; 
brown  or  chocolate.  A  little  glue  is  mixed  with  the  two 
first  colors,  and  gum  only  with  the  others.  The  colors 
used  are  mostly  earths  or  minerals,  as  other  will  not 
stand  the  action  of  the  lime.  Vegetable  pigments  can- 
not be  used  for  this  model  of  painting,  even  when  mixed 
with  mineral  pigments,  and  of  the  latter  only  these  are 
available  which  resist  the  chemical  action  of  the  lime. 
The  lime  in  drying  throws  out  a  kind  of  crystal  surface 
which  protects  the  color  and  imparts  a  degree  of  clear- 
ness superior  to  that  of  any  work  in  tempera  or  size 
paint.  The  process,  although  apparently  simple,  re- 
quires dexterity  and  certainty  of  hand,  for  the  surface 
of  the  plaster  is  delicate,  and  the  lime  only  imbibes  a 
certain  quantity  of  additional  moisture  in  the  form  of 
liquid  colors,  after  which  it  loses  its  crystallizing  quality, 
and  the  surface  or  a  portion  of  it  becomes  rotten.  It  is 
only  after  the  lime  has  dried  that  such  flaws  are  dis- 
covered, and  the  only  remedy  is  to  cut  away  the  de- 


260  CEMENTS  AND  CONCRETES 


fective  portion,  lay  on  fresh  plaster  and  do  the  work 
over  again.  The  colors  become  lighter  after  the  plaster 
dries,  so  allowance  must  be  made  for  this.  The  advan- 
tages which  this  process  possesses  are  clearness,  exhib- 
iting the  colors  in  a  pure  and  bright  state ;  the  surface 
is  not  dull  and  dry  as  in  tempera  or  size  painting,  nor 
glossy  as  in  oil  painting;  it  can  be  easily  seen  from  any 
point,  and  it  is  not  injured  by  exposure  to  the  air;  it 
will  stand  washing,  and  can  be  cleansed  with  water  with- 
out injury/' 

SCAGLIOLA. 

Historical. — Scagliola  derives  its  name  from  the  use 
of  a  great  number  of  small  pieces  or  splinters ;  scagliole 
of  marble  being  used  in  the  best  description  of  this 
work.  It  is  said  to  have  been  invented  in  the  early  part 
of  the  sixteenth  century  by  Guido  Sassi,  of  Cari,  in 
Lombardy,  but  it  is  more  probable  that  he  revived  an 
old  process,  and  introduced  a  greater  variety  of  colors 
in  the  small  pieces  of  marble  and  alabaster  used  to 
harden  the  surface,  and  better  imitate  real  and  rare 
marbles.  It  is  sometimes  called  mischia  from  the  many 
mixtures  of  colors  introduced  by  it.  The  use  of  colored 
plaster  for  imitating  marbles  was  known  to  the  ancients, 
although  the  pure  white,  or  marmoratum  opus  and  al- 
hariim  opus,  mentioned  by  Pliny,  was  more  used.  The 
plastic  materials  used  by  the  Egyptians  in  coating  the 
walls  of  their  tombs  partook  of  the  nature  of  marble. 
The  ancients  also  ased  a  marble-like  plaster  for  lining  the 
bottoms  and  sides  of  their  aqueducts,  which  has  endured 
for  many  centuries  without  spoiling  or  cracking.  In  the 
decoration  of  their  domes  the  Moors  used  colored 
plasters,  which  have  stood  the  ravages  of  time.  The 


MISCELLANEOUS  MATTERS 


261 


beautiful  chunam  or  plaster  of  India,  as  used  by  the 
natives,  has  a  hard  surface,  takes  a  brilliant  polish  rival- 
ling that  of  real  marble,  and  has  withstood  for  many 
ages  the  sun  and  weather  without  sign  of  decay.  The 
roofs  and  floors  of  many  houses  in  Venice  are  coated  with 
smooth  and  polished  plaster,  made  at  a  later  date,  strong 
enough  to  resist  the  effects  of  wear  and  weather, 
without  visible  signs  of  crack  or  flaw,  and  without  much 
injury  from  the  foot.  Scagliola  was  largely  employed 
by  the  Florentines  in  some  of  their  most  elaborate  works. 
It  has  been  used  in  France  with  great  success  for  archi- 
tectural embellishment.  The  rooms  are  so  finished  that 
no  additional  work  in  the  shape  of  house-painting  is 
required,  the  polish  of  the  plaster  and  its  evenness  of 
tint  rivalling  porcelain.  Scagliola  is  the  material  used. 
At  times  the  surface  of  the  plaster  is  fluted,  or  various 
designs  are  executed  in  intaglio  upon  it  in  the  most 
beautiful  manner. 

Scagliola  is  one  of  the  most  beautiful  parts  of  decora- 
tive plaster  work,  and  it  is  regrettable  that  there  should 
not  be  a  greater  revival  of  such  a  charming  and  beautiful 
art.  Its  limited  use  in  recent  times  is  greatly  owing  to 
its  manufacture  being  restricted  by  rules  and  rigid 
methods  and  even  prejudices,  and  being  confined  to 
monopolists,  who  kept  the  method  secret  until  it  was 
looked  upon  as  a  mystery  which  greatly  enhanced  its 
cost.  But  through  the  information  now  at  hand,  com- 
bined with  a  little  practical  experience  and  enterprise, 
there  is  no  valid  reason  why  architects  should  not  adopt 
it  for  second  or  even  for  third  class  buildings.  It 
possesses  great  beauty,  and  is  capable  of  affording  grand 
effects  and  the  richest  embellishments  in  architecture. 
Scagliola,  in  skilful  hands,  can  be  produced  in  every 
variety  of  color  and  shade,  in  every  possible  pattern,  in 


262  CEMENTS  AND  CONCRETES 


every  conceivable  form  and  size,  from  a  paper  weight 
to  the  superficial  area  of  a  large  wall.  It  can  be  made 
at  a  price  that  would  enable  it  to  take  the  place  of  the 
most  durable  material  now  in  use.  Experience  has 
proved  that  it  will  last  as  long  as  the  house  it  adorns, 
and  with  an  occasional  cleaning,  it  will  always  retain  its 
polish  and  beauty.  It  has  been  produced  in  past  days 
in  our  own  and  other  lands,  and  carried  to  such  high  ex- 
cellence, that  many  of  the  precious  marbles,  such  as 
jasper,  verd  antique,  porphyry,  brocatello,  giailo  an- 
tique. Sienna,  etc.,  have  been  imitated  so  minutely,  and 
with  an  astonishing  degree  of  perfection,  as  to  defy  de- 
tection. It  will  not  only  retain  its  polish  for  years,  but 
can  be  renovated  at  much  less  comparative  cost  than 
painting  and  varnishing  marbled  wood,  or  plaster  work. 
It  is  cheaper  and  more  satisfactory  to  use  scagliola  in 
the  first  instance  than  to  go  to  the  expense  of  plastering 
walls,  columns,  etc.,  with  Keen's  or  other  kindred  ce- 
ments, used  for  their  hardness  and  ready  reception  of 
paint,  which  are  to  be  afterwards  marbled  and  var- 
nished. Both  are  imitations,  but  painted  marble  can 
never  be  compared  with  scagliola,  which  has  the  look, 
color,  touch,  and  polish  of  the  more  costly  natural 
marbles. 

Various  Artificial  Marbles. — Various  patents  have 
been  taken  out  for  the  production  of  artificial  marbles, 
having  for  their  bases  plaster  of  Paris.  These  patents 
will  be  briefly  mentioned  here. 

Evaux 's  Artificial  Marble  is  composed  of  plaster  mixed 
with  albumen  and  mineral  colors,  the  ground  being  zinc 
white.  Rowbotham  also  employed  plaster  and  albumen 
soaked  in  a  solution  of  tannic  acid.  Lilienthal  makes 
an  artificial  marble  with  Keen 's  cement,  slaked  lime,  and 
curdled  milk. 


MISCELLANEOUS  MATTERS  263 


Pick^s  Neoplaster/^ — This  composition  was  patented 
in  1883,  and  is  composed  of  75  per  cent,  of  plaster,  mixed 
with  feldspar,  marl,  coke  dust,  and  pumice-stone.  Gule- 
ton  and  Sandeman  patented  an  artificial  marble  in  1876. 
It  is  composed  of  Keen's  cement  backed  with  fibre,  and 
soaked  or  brushed  on  the  back  with  a  solution  of  as- 
phalt. The  slabs  were  made  in  glass  moulds.  La- 
roque's  patent  marble  is  formed  of  plaster  and  alum 
gauged  with  gum  water,  the  veining  being  done  with 
threads  of  silk  dipped  in  the  required  colors.  The 
backs  of  the  slabs  or  panels  are  strengthened  with  can- 
vas. 

Mur  Marble  is  composed  of  a  mixture  of  Keen's  and 
Marin's  cement  in  equal  proportions,  made  into  a  paste, 
with  a  solution  of  sulphate  of  iron  and  a  small  quanti- 
ty of  nitric  acid  in  water.  The  slabs  are  dried  and 
tarred  at  a  temperature  of  250  degrees  F.  for  about 
twenty  hours,  and  when  cool  are  rubbed,  colored,  var- 
nished, or  japanned,  as  required.  There  is  another 
patent  formed  of  plaster,  gauged  with  a  solution  con- 
taining tungstate  of  soda,  tartaric  acid,  bicarbonate  of 
soda,  and  tartarate  of  potash.  Another  is  composed  of 
Keen's  cement  10  parts,  ground  glass  1  part,  and  alum 
%  part,  dissolved  in  hot  water. 

Guattaris  Marble  is  obtained  by  transforming  gypsum 
(sulphate  of  lime)  into  carbonate  of  lime  (marble). 
There  are  two  methods.  The  first  consists  of  dehy- 
drating blocks  of  gypsum,  and  then  hardening  by  im- 
mersion in  baths  containing  solutions  of  silicate  of  soda, 
silicate  of  lime,  chloride  of  lime,  sulphate  of  potash, 
soda,  acid  phosphate  of  lime,  etc.  The  blocks  are  cut 
into  slabs  or  carved  before  being  put  into  the  bath.  The 
second  method  consists  in  dehydrating  the  gypsum,  and 
bathing  in  some  of  the  above  chemicals.    They  are  then 


264  CEMENTS  AND  CONCRETES 


dried  and  burnt  at  a  red  heat^  and  allowed  to  cool. 
After  a  second  burning;  and  cooling,  the  products  are 
ground  as  for  plaster.  This  powder  is  called  '^Marmo- 
rite''.  The  marmorite  is  gauged  in  a  trough  with  some  of 
the  water  from  the  baths  as  above,  kneaded  into  a  paste, 
and  the  colors  added  and  mixed.  The  paste  is  then  put  in- 
to moulds  and  pressed,  and  when  set  they  are  taken  out, 
dried,  and  finally  polished.  Mineral  colors  are  used. 
Yellow  and  its  tints  are  obtained  with  citrate  of  iron 
dissolved  in  oxysulphate  of  iron,  sulphate  of  cadmium, 
chloride  of  yttrium,  chromate  of  lithium,  and  yellow  of 
antimony.  Red  and  its  tints  are  obtained  with  dragon's 
blood,  sesquioxide  of  iron,  mussaride  red,  and  sulphate 
of  didymium,  and  the  salts  derived  from  it,  which  give 
a  rose  color.  Azure  blue  is  obtained  with  sulphate  of 
sodium  mixed  with  acetate  of  copper  and  tartaric  acid 
and  oxide  of  cobalt.  Green  and  its  tints  are  obtained 
with  verdigris,  hydrochlorate  of  cobalt.  Black  is  ob- 
tained by  pyrolignite  of  iron  reduced  by  boiling  in  gallic 
acid  with  sirco  black.  Black  marble  is  also  obtained 
by  immersing  gypsum  blocks  or  slabs  or  the  cast  mar- 
morite in  a  hot  preparation  of  bitumen.  During  this 
operation  the  dehydration  of  the  material  under  treat- 
ment is  accomplished,  and  the  bitumen  not  only  pene- 
trates the  mass,  but  fills  up  all  the  pores  and  spaces 
evacuated  by  the  water  which  was  contained  in  the  ma- 
terial treated,  and  a  hard  mass  of  brilliant  black  is  ob- 
tained in  every  way  equal  to  Flanders  marble.  It  is 
said  that  the  above  imitation  marbles  are  largely  used  in 
Florence. 

Scagliola  Manufacture. — Scagliola  can  be  made  in  situ 
or  in  the  work  shop,  according  to  the  requirements  of  the 
work;  but  in  either  case  it  is  necessary  that  the  work 
place  should  be  kept  at  a  warm  temperature,  and  the 


MISCELLANEOUS  MATTERS  265 


work  protected  from  dust  or  damp  atmosphere.  The 
plaster  should  be  the  strongest  and  finest  in  quality,  and 
free  from  saline  impurities.  It  should  be  well  sifted  to 
free  it  from  lumps  or  coarse  grains,  which  otherwise 
would  appear  as  small  specks  of  white  in  the  midst  of 
the  dark  colors  when  the  polishing  is  completed.  Glue 
water  should  be  made  in  small  quantities,  or  as  much  as 
will  suffice  for  the  day,  as  it  deteriorates  if  kept  too  long. 
Glue  tends  to  harden  the  plaster,  and  gives  gloss  to  the 
surface.  Unfortunately  it  is  also  the  cause  of  its  sub- 
sequent dullness  and  decay  when  exposed  to  moisture 
and  damp  air,  hence  the  necessity  of  using  the  best  glue, 
good  and  fresh  glue  water.  If  scagliola  is  required  to  be 
done  in  situ  on  brick  walls,  the  joints  should  be  well 
raked  out  and  the  walls  well  wetted.  This  gives  a  good 
key,  stops  the  excessive  absorption,  and  partly  prevents 
the  evil  effects  of  saline  matters,  that  are  found  in  most 
kinds  of  new  bricks.  These  saline  matters  are  the  prin- 
cipal cause  of  subsequent  efflorescence  which  sometimes 
appears  on  plastic  surfaces,  and  is  so  unsightly  and  dis- 
astrous to  surface  decorations.  Saline  matters  are  also 
caused  by  acids,  used  in  the  manufacture  of  some  ce- 
ments. Saline  is  also  found  in  mortars  made  with  sea 
water,  or  with  unwashed  sea  sand.  These  impurities 
can  be  avoided  by  carefully  selecting,  mixing,  and  work- 
ing of  the  materials.  Brick  walls  for  scagliola  should 
be  allowed  to  stand  as  long  as  possible,  and  wetted  at  in- 
tervals. This  allows  more  time  for  the  saline  to  exude 
and  be  washed  off.  The  exudation  may  be  hastened  or 
the  salts  absorbed  and  killed  by  brushing  the  walls  with 
^a  solutiQn  of  freshly  slaked  lime.  This  is  allowed  to  stand 
until  dry,  and  then  cleaned  off  by  scrubbing  with  warm 
water  and  a  coarse  broom.  If  space  permits,  a  wall  bat- 
tened and  lathed  is  the  best  preventive.    Scagliola  slabs, 


266  CEMENTS  AND  CONCRETES 


screwed  to  plugs  or  battens,  are  protected  from  saline 
and  internal  damp. 

Iron  columns  to  support  overhead  weights,  and  fixed 
as  the  building  proceeds,  are  often  covered  with  scaglio- 
la.  If  the  work  is  done  in  situ,  the  iron  core  is  sur- 
rounded with  a  wood  skeleton  and  strong  laths,  or  paint- 
ed wire  lathing.  The  wood  templates  are  cut,  equal  to 
the  lower  and  upper  diameters  of  the  columns,  and  one 
fixed  at  the  top  and  bottom  of  the  shaft.  The  ground 
work  is  then  ruled  fair  with  a  diminished  floating  rule. 
This  gives  a  guide  and  equal  thickness  for  the  scag  (the 
trade  abbreviation  for  scagliola  stuff). 

The  floating  coat  is  composed  of  the  best  and  strong- 
est plaster  procurable,  and  gauged  as  stiff  as  possible 
with  sufficient  strong  size  water,  so  that  it  will  take  from 
twelve  to  twenty-four  hours  to  set.  The  floating  is  gen- 
erally brought  out  from  the  lath  in  one  coat.  A  tenth 
part  of  well-washed  hair  is  sometimes  mixed  with  the 
gauged  plaster,  to  give  greater  toughness  and  tenacity. 
The  surface  must  be  carefully  scratched  with  a  singly- 
pointed  lath,  to  give  a  sound  and  regular  key  for  the 
scag,  which  is  laid  on  in  slices,  and  pressed  and  beaten 
with  a  stiffish,  square  pointed  gauging  trowel,  somewhat 
like  a  margin  trowel.  The  scag  is  laid  about  %  inch 
fuller  than  the  outline,  and  when  set,  the  surface  is 
worked  down  with  a  "toothed  plane."  This  plane  is 
similar  to  that  used  by  cabinetmakers  for  veneering  pur- 
poses. The  irons  are  toothed  in  various  degrees  of  fine- 
ness, and  set  at  an  angle  of  70  degrees.  If  the  columns 
are  fluted,  a  half-pound  plane  is  required  for  the  flutes. 
As  the  planing  proceeds,  the  outline  is  tested  at  inter- 
vals with  a  rule,  as  a  mason  does  in  using  a  straight- 
edge when  working  mouldings.  A  planed  or  chisel-cut 
surface  shows  up  the  grain  and  figure  of  the  marble 


MISCELLANEOUS  MATTERS  267 


much  better  than  if  ruled.  A  rule  is  apt  to  work  out  or 
otherwise  spoil  the  figure  of  most  marbles.  The  beating 
on  the  slices  may  disturb  the  figure  of  the  marble  at  the 
outer  surface,  but  if  the  scag  is  gauged  stiff,  the  inner 
portion  will  be  intact,  hence  the  advantage  of  planing. 
To  obtain  greater  cohesion  between  the  scag  and  the 
floating,  the  latter  is  brushed  with  soft  gauged  stuff  just 
before  each  piece  of  the  former  is  laid.  The  scratching 
is  also  filled  up  at  the  same  time,  so  as  to  obtain  the  full 
power  of  the  key  with  the  least  amount  of  pressing  on 
and  beating  the  scag  slices  in  position.  When  the  shaft 
is  planed,  the  wood  colors  are  taken  off;  then  the  base 
and  necking  moulding,  which  has  been  previously  cast, 
are  screwed  in  position,  using  plaster  (colored  the  same 
as  the  ground  of  the  marble)  for  the  joints.  When  dry, 
the  whole  is  stoned  and  polished.  Pilasters  or  other 
surface  work  done  in  situ  are  executed  by  similar  pro- 
cesses. Cast  and  turned  work  should  always  be  support- 
ed by  strong  wooden,  frames,  formed  with  ribs,  and  cov- 
ered with  ^  inch  to  i^^h  thick  sawn  laths.  The 
strength  of  the  frames  is  regulated  according  to  the  posi- 
tion and  purpose  of  the  intended  work.  For  example,  a 
column  with  base  placed  on  a  square  pedestal  would  not 
require  so  strong  framing  as  the  pedestal  which  has  to 
support  the  column  and  base.  Also  being  on  the  floor 
level,  it  is  more  exposed  to  contact  and  pressure.  Fram- 
ing is  also  necessary  for  fixing  purposes,  and  to  allow 
for  the  work  being  handled  freely  when  being  moved 
from  the  work  shop  to  the  building,  and  when  being 
fixed.  Small  work  may  be  made  without  framing. 
Turned  columns  are  framed  in  two  different  methods, 
each  way  being  for  a  special  purpose.  If  it  is  an  ^'in- 
dependent column'',  or  in  other  words  a  complete  col- 
umn, not  intended  to  surround  a  brick  or  iron  core,  the 


268  CEMENTS  AND  CONCRETES 


frame  is  made  lighter  and  thinner,  and  in  such  ways  as 
to  admit  the  column  to  be  cut  either  in  two  equal  parts, 
or  with  one-third  out,  or  just  as  much  as  will  allow  the 
larger  part  to  pass  over  the  iron  core.  Care  must  be 
taken  that  the  inner  diameter  of  the  skeleton  frame  is 
greater  than  the  diameter  of  the  iron  core.  This  is  to 
allow  for  fixing.  The  outer  diameter  of  the  frame  is  made 
about  1  inch  less  than  the  finished  outline  of  column,  to 
allow  %  inch  for  the  core  and  ^  inch  for  the  scag.  The 
two  parts  of  the  frame  are  fixed  with  wooden  pegs  (not 
nails),  so  that  they  may  be  sawn  when  the  column  is  cut 
into  halves.  This  is  not  done  until  the  column  is  pol- 
ished and  ready  for  fixing.  The  parts  are  best  separated 
by  cutting  with  a  thin  and  fine-toothed  saw.  The  thin- 
ner the  cut  the  better  the  joint.  The  two  parts  are 
fixed  on  the  iron  core  with  brass  screws  or  clamps,  from 
3  to  4  feet  apart,  and  the  joints  made  good  with  colored 
plaster  as  before.  Sometimes  a  zigzag  joint  is  made,  the 
one  side  fitting  the  other,  to  give  the  marble  or  figure  a 
more  regular  and  natural  appearance.  The  joints  are 
then  stopped  with  various  tints,  these  being  the  same 
gauge  as  used  for  the  face. 

Sometimes  the  framing  is  made  longer  than  the  shaft, 
so  as  to  project  at  each  end.  These  projecting  parts  are 
used  as  fixing  points  for  screws,  and  binding  round  with 
hoop-iron  before  the  plinth  and  cap  are  fixed.  These 
parts  project  the  edges  of  the  work  while  being  moved 
and  fixed.  Considerable  skill  and  patience  is  required 
to  make  a  strong  joint,  well  polished,  and  imperceptiKe 
to  the  eye.  The  frames  are  made  with  solid  ends,  with 
a  square  hole  in  each  to  fit  the  spindle.  The  solid  ends 
are  cut  out  of  inch  deal,  and  are  used  to  keep  the  skele- 
ton firm  and  in  a  central  position  when  the  spindle  is 
turning  on  its  bearings.    One  of  the  ends  is  fixed  to 


MISCELLANEOUS  MATTERS  269 


flange  of  the  spindle  with  screws.  If  a  case  column  is 
being  made,  the  solid  ends  are  taken  off  before  the  col- 
umn is  cut ;  but  they  form  permanent  parts  of  the  fram- 
ing for  an  independent  column.  The  mould  is  fixed  at 
one  side,  and  level  with  the  centre  of  the  spindle,  which 
is  the  centre  of  the  column's  diameter.  Care  must  be 
taken  that  the  profile  of  the  mould  plate  to  the  centre 
of  the  spindle  is  one-half  of  the  required  diameter  at 
each  end  of  the  shaft. 

Vases  are  generally  made  without  wood  framing.  They 
are  turned  on  a  spindle  with  a  plaster  core  screwed  to  the 
flange  in  the  form  of  a  parabola,  to  give  the  form  of  the 
hollow  inside.  On  the  core  a  coat  of  scag  is  laid  and  al- 
lowed to  set.  This  is  scratched  to  give  a  key  for  the 
coarse  plaster  w^hich  forms  the  body  of  the  vase.  This 
is  formed  to  the  desired  outer  profile  by  means  of  a 
mould  fixed  on  the  outside,  and  muffled  to  allow  for  a 
thickness  of  outside  scag.  When  the  core  is  run,  the 
muffle  is  taken  off,  and  the  scag  laid,  keeping  it  about  % 
inch  thicker  than  the  true  profile,  to  allow  for  turning 
and  stoning.  When  the  scag  is  set,  it  is  turned,  and 
then  the  vase  is  taken  off  the  spindle  and  plaster  core. 
The  spindle  hole  is  used  as  a  key  for  a  slate  or  iron  dowel 
for  fixing  the  vase  on  to  the  square  plinth.  The  vase  is 
then  polished.  Cheap  work  is  usually  run  or  turned 
with  a  mould.  This  is  done  to  save  turning  with  chisels, 
but  it  spoils  the  true  figure  of  most  marbles. 

A  more  recent  way  of  imitating  marbles  is  known  by 
the  name  of  Marezzo,  which  does  not  require  so  much 
polishing,  being  made  on  plate  glass  or  other  smooth 
surface.  Keen's  superfine  plaster  is  used.  The  mode 
of  making  Marezzo  is  described  later  on.  Specimens  of 
the  real  marbles^  to  give  the  color  and  form  of  veining, 


270  CEMENTS  AND  CONCRETES 


spots,  and  figures,  will  be  of  great  service  to  the  be- 
ginner. 

Mixing. — Mixing  the  colors  is  an  important  part  of 
scagliola  manufacture,  and  the  following  colors,  mixing 
and  mode  of  using,  will  serve  as  an  index  for  the  imi- 
tating of  any  other  marble  that  is  not  detailed.  Fine 
plaster  (not  cement)  is  used  for  making  the  best  class 
of  scagliola,  gauged  with  sized  water,  which  is  made  by 
dissolving  1  lb.  of  best  glue  with  7  quarts  of  water.  (This 
is  known  in  the  trade  as  strong  water".)  The  stuff, 
when  gauged  will  take  about  six  hours  to  set.  All  mix- 
ing is  done  on  a  clean  marble  or  slate  slab.  One  of  the 
principal  arts  is  the  mixing,  but  there  are  no  two  men 
who  mix  exactly  alike,  and  it  is  largely  a  matter  of  ex- 
perience. The  chopping  or  cutting  into  slices  with  a 
knife  is  another  important  point  in  the  mixing,  apart 
of  course  from  the  special  colors.  Where  there  are  two 
shades  of  one  color  in  any  given  work,  the  cutting  does 
not  affect  their  original  shade.  No  dry  color  is  used, 
only  ground  water-colors.  The  beginner  had  better  ex- 
periment with  a  small  sample  of  ^^Penzatti"  or  Pen- 
zance marble.  With  one  gill  of  size  w^ater,  gauge  plaster 
middling  stiff,  then  mix  thoroughly  with  the  gauged 
plaster  a  little  red.  Do  the  same  Avith  a  little  black. 
(See  quantities  below.)  Blend  this  stuff  properly  by 
working  it  on  the  bench  with  the  hands  (not  tools),  then 
roll  it  out,  and  cut  it  into  slices  about  one  inch  thick. 
Take  up  these  slices,  and  part  them  with  the  fingers 
about  the  size  of  a  walnut,  and  put  them  aside,  a  little 
distance  apart,  on  a  bench. 

The  veining  in  this  instance  is  white.  Over  these  little 
lumps  scatter  half  a  handful  of  crumbs,  made  by  re- 
serving a  little  of  the  gauged  plaster,  and  making  it 
crumbly  with  dry  plaster,  mixing  with  it  a  few  small 


MISCELLANEOUS  MATTERS  271 


bits  of  alabaster  or  marble.  Then  gauge  a  little  plaster 
in  a  basin,  with  a  tooth  brush,  about  2  inches  wide,  dip 
into  this  gauged  plaster,  and  smudge  the  little  lumps  all 
over  with  it.  Knock  these  lumps  together  into  a  big  one, 
and  chop  the  big  lump  three  times.  (This  chopping 
means  cutting  with  a  knife  into  slices  once,  and  knock- 
ing up  again;  cutting  with  a  knife  a  second  time,  and 
knocking  up  again ;  and  then  cutting  with  a  knife  a  third 
time,  when  it  is  finished.)  This  lump  is  then  ready  to 
be  cut  into  slices,  and  applied  to  any  purpose  required; 
but  in  this  case,  being  wanted  for  a  specimen,  it  is  cut 
into  slices  about  %  inch  thick,  and  laid  close  together 
flat  on  a  sheet  of  paper,  and  allowed  to  remain  until  set. 
It  is  then  planed,  and  when  dry  polished.  This  opera- 
tion is  an  embodiment  of  the  principle  of  ''scag"  mix- 
ing nearly  from  beginning  to  end,  only  submitting  one 
color  for  another  for  the  various  marbles.  The  mixing 
is  generally  known  as  plain  and  rich,  and  may  be 
described  thus:  Take  a  Sienna  pedestal,  for  instance. 
Two  shades  of  sienna,  plain  mixing;  one  or  two  shades 
of  dark  with  veining,  rich  mixing,  both  done  on  the  same 
principle  as  Penzatti.  They  are  cut  into  slices  and  laid 
on  alternately.  All  veining  of  any  color  is  done  as 
described  above,  only  modified  by  the  consideration  that 
if  strong  veining  is  wanted  the  stuff  must  be  stiffish,  and 
for  fine  veining  it  must  be  slightly  softer.  Various-sized 
measures  for  the  water  and  scales  for  weighing  the  color 
should  be  used.  Pats  of  each  gauge  should  be  set  aside 
as  test  pats  to  determine  when  the  main  portion  of  stuff 
is  set.  It  is  advisable  to  number  the  pats  for  future 
reference  as  to  quantity  of  colors,  time  of  setting,  and 
tints  when  dry.  The  various  colors  and  tints  are  gauged 
and  chopped  as  previously  described,  and  according  to 
the  marble  required.    The  core  being  laid  on  the  skele- 


272  CEMENTS  AND  CONCRETES 


ton,  and  left  in  a  keyed  and  rough  state  until  dry  and 
expansion  ceased,  it  is  ready  when  set  for  the  scag.  The 
core  is  now  damped  and  well  brushed  with  the  white  or 
other  vein  that  has  to  be  made.  The  veining  is  gauged 
thin,  and  being  brushed  and  laid  in  the  core,  will  tend  to 
make  the  slices  adhere  better,  and  fill  up  the  interstices 
caused  by  the  jagged  edges  of  the  cut  slices.  The  slices 
are  then  taken  and  pressed  firmly  onto  the  core,  arrang- 
ing in  proportion  to  the  figure  of  the  marble.  To  render 
the  work  more  dense^  beat-  it  with  a  fiat-faced  mallet 
and  a  large  gauging  trowel  with  a  square  end.  Try  the 
work  with  a  rule  to  see  if  the  surface  is  fair.  The 
rough  surface  should  not  be  less  than  %  inch  thicker 
than  the  true  line  of  the  work,  to  allow  for  planing  and 
stoning.  When  required,  pieces  of  alabaster  are  inserted 
before  the  stuff  is  set.  Metallic  ores  are  used  in 
some  marbles,  also  pieces  of  granite  and  real 
marble.  When  the  scag  is  laid^  the  work  is  left  until 
set  and  dry.  It  is  then  planed  stopped,  stoned  and 
polished.  Columns  and  circular  work  are  turned  on  a 
lathe,  and  the  rough  surface  reduced  to  the  true  profile 
with  long  chisels  similar  to  those  for  turning  wood  or 
other  materials.  This  should  not  be  attempted  until  the 
materials  are  thoroughly  set. 

Colors  mid  Quantities. — The  following  are  the  colors 
and  quantities  used  for  various  marbles.  The  propor- 
tions of  strong  water,  which  is  made  varies,  the  due 
quantity  should  be  tested  by  gauging  small  pats  of 
plaster  to  ascertain  the  time  of  setting.  As  the  tints  of 
real  marble  vary  in  some  species,  the  mixing  must  to 
some  extent  be  left  to  the  ingenuity  of  the  workman. 
With  a  little  practice  and  perseverance,  a  careful  and 
observant  man  will  soon  succeed  in  getting  the  required 
tints. 


MISCELLANEOUS  MATTERS 


273 


Penzance  Marble. — 10  oz.  of  light  purple  brown  to  1 
pint.  Veining  (plain  mixing),  2  oz.  black  to  1  gill;  vein- 
ing  (rich  mixing)  5  oz.  black  to  1/2  pint;  veining  (rich 
mixing),  1  oz.  black  to  I/2  gill.  All  liquid  measurements 
refer  to  strong  water. 

Egyptian  Green. — 5  oz.  black  to  1  pint.  Veining,  i/^  oz. 
green  to  %  pint  light  shade ;  veining,  i/4  oz.  green  to  I/2 
gill.  White  the  same,  black  chopped  three  times ;  a  few 
black  spots  same  as  brown  Beige. 

Brown  Beige. — Four  shades — 1  light  purple  brown 
(indigo) ;  2  middle  shades  (blue  black)  ;  1  very  dark 
shade  (vegetable  black).  Veining,  burnt  sienna  with  red 
alabaster  spots — 4  oz.  (light  shade)  to  ^  pint;  4  oz. 
(middle)  to  %  pint;  4  oz.  (very  dark)  to  i/^  pint; 
Y2  oz.  burnt  sienna  to  pint ;  1/4  oz.  black  to  i/4  pint ; 
^2  piiit  for  the  grey  with  crumbs,  and  red  alabaster 
spots'. 

Dark  Porphyry. — Color,  light  purple  brown,  with 
black,  and  a  little  ultramarine,  blue  spots,  black,  ver- 
milion grey,  and  a  little  red. 

Green  Genoa. — 214  oz.  green  to  i/^  pint  (rich  mix- 
ing.) ;  5  OZ.  black  to  1  pint.  Veining,  l^  oz.  green  to  14 
pint.  White  veining  the  same,  with  alabaster  spots,  and 
black. 

Rouge  Boyale. — Color,  light  purple  brown,  with  a  little 
sienna,  and  umber,  with  ultramarine,  blue  or  blue  black. 
Vert-Vert. — 1/4  oz.  green  to  I/2  pint;  dark  green  with 
sienna;  dry  green  plaster. 

Devonshire  Bed  Marble. — All  sienna  work.  Light 
mixing — 1  shade  grey;  1  shade  lemon  chrome;  1  shade 
light  purple  brown;  1  shade  flesh  color;  veining  burnt 
sienna.  Dark  mixing.\ — 1  shade  light  purple  brown, 
with  indigo  blue  in  it;  1  shade  dark  purple  brown;  1 
shade  middling  purple  brown;  1  shade  grey;  1  shade 


274 


CEMENTS  AND  CONCRETES 


lemon  chrome.  Veining,  burnt  sienna,  with  small  ala- 
baster spots. 

Sienna  Mixing, — 5  oz.  sienna  to  I/2  pint,  dark  shade; 
3  oz.  sienna  to  I/2  pint,  middle  shade;  2  oz.  sienna  to 
1/2  pint,  light  shade. 

Griotte  Marhle. — 10  oz.  of  light  purple  brown  to  1 
pint  5  oz.  of  dark  purple  brown  to  %  pint,  with  ala- 
baster spots.    Ground  with  red  veins,  and  small  spots. 

Spanish  Buff. — Burnt  sienna,  2  shades,  with  large  ala- 
baster spots.  Veining,  white  and  blue  black,  with  small 
alabaster  spots.    Ground  with  red  veins,  and  blue  spots. 

Light  Verd  Antique. — 2I/2  oz.  green  to  Yo  pint; 
iy2  oz.  black  to  1  gill ;  I/2  gill  black  to  1  gill  grey  shade. 

Dark  Verd  Antique. — Green  spots  cut;  grey  spots  cut ; 
black  spots  with  green  and  grey.  Veining  2^/2  oz.  green 
to  1/2  pint  (rich  mixing)  ;  2%  oz.  dark  green  to  I/2  pint 
(rich  mixing)  ;  1/4  oz.  black  to  I/2  pint  (rich  mixing). 

Plain  mixing,  same  as  above,  with  small  alabaster 
spots,  and  small  black  spots. 

Black  and  Gold. — 5  oz.  of  black  to  1  pint.  Veining, 

2  shades  dark  sienna  to  I/2  pint  (rich  mixing)  ;  2  shades 
light  to  1/^  pint  (rich  mixing)  ;  2  parts  light  and  grey, 
with  alabaster  spots,  and  crumbs.  Veining  must  be  stiff ; 

3  oz.  of  black  to  1  gill. 

Walnut. — 2  parts  burnt  umber;  1  part  rose  pink. 

Ve7^ta  Alps  Marhle. — 5  oz.  black  to  1  pint.  Veining, 
114  oz.  of  green  to  li/4  gills;  14  oz.  green  to  1/2  gill,  with 
black  crumbs  chopped  three  times  for  the  ground. 

Rosse  De  La  Vantz  Marble. — Rich  mixing  with  indi- 
go blue — 1  shade  light  purple  brown ;  1  shade  dark  pur- 
ple brown;  1  shade  Venetian  red.  Veining,  black  for 
the  ground,  and  white  and  green  veining  for  the  mixing, 
with  alabaster  spots  and  crumbs. 


MISCELLANEOUS  MATTERS 


275 


Polishing  White  Scagliola. — White  scagliola  is  often 
made  with  superfine  Keen's  cement.  A  small  portion  of 
mineral  green  or  ultramarine  blue  is  added  to  improve 
and  indurate  the  white  color.  White  work  requires  spe- 
cial care  to  prevent  discoloration  or  specks.  When  the 
work  is  left  for  drying  purposes,  or  at  the  end  of  the  day, 
it  should  be  covered  up  with  clean  cotton  cloths  to  pre- 
vent the  ingress  of  dust,  smoke  or  being  touched  with 
dirty  hands.  The  tools  should  be  bright  and  clean.  Steel 
tools  should  be  as  sparingly  used  as  possible.  When  the 
cement  has  thoroughly  set  and  the  work  is  hard,  it  is 
rubbed  down  with  pumice-stone,  or  finely  grained  grit- 
stone, by  the  aid  of  a  sponge  and  clean  water,  rubbing 
lightly  and  evenly  until  the  surface  is  perfectly  true.  It 
is  then  stoned  with  snake-water  (Water  of  Ayr),  using 
the  sponge  freely  and  the  water  sparingly  until  all  the 
scratches  disappear.  Afterwards  well  sponge  the  sur- 
face until  free  from  glue  and  moisture.  It  is  now  ready 
for  the  first  stopping.  Stopping  is  an  important  part  of 
the  polishing  process,  and  should  be  carefully  and  well 
done,  to  ensure  a  good,  sound,  and  durable  polish. 

First  gauge  a  sufficient  quantity  of  cement  and  clean 
water  in  a  clean  earthenware  gauge-pot.  The  gauged 
stuff  should  be  about  the  consistency  of  thick  cream.  It 
is  well  dubbed  in,  and  brushed  into  and  over  the  surface, 
taking  care  that  no  holes  or  blubs  are  left.  When  the 
stuff  on  the  face  gets  a  little  stiff,  scrape  off  the  super- 
fluous stopping  with  a  hard-wood  scraper  having  a  sharp 
edge.  Then  repeat  the  brushing  (but  not  the  dubbing) 
with  the  soft  gauged  stuff,  and  scraping  two  or  three 
times,  or  until  the  surface  is  solid  and  sound.  The  work 
is  now  left  until  the  cement  is  perfectly  set.  It  is  then 
stoned  again  for  the  third  time  with  a  piece  of  fine  snake- 
stone,  and  stopped  as  before,  with  the  exception  that  the 


276  CEMENTS  AND  CONCRETES 


superfine  stopping  is  not  scraped  off,  but  wiped  off  with 
soft  clean  rags.  The  work  is  left  until  the  cement  is  set 
and  the  surface  dry.  It  is  then  polished  with  putty 
powder  (oxide  of  tin),  which  is  rubbed  over  the  surface 
with  soft  clean  white  rags,  damped  with  clean  water.  In 
polishing  mouldings,  the  stone  must  be  cut  or  filed  to  fit 
each  separate  member  of  the  moulding. 

Polishing  Scagliola. — The  polishing  of  scagliola  is 
slightly  different.  It  is  rubbed  down  with  a  soft  seconds 
(marble  grit)  or  gritty  stone,  using  the  sponge  and  water 
freely  until  the  surface  is  true.  The  glut  and  glue  are 
cleaned  off  with  a  brush  and  sponge,  using  plenty  of 
water,  until  the  pores  are  free  from  grit.  The  moisture 
is  sponged  off,  and  the  work  left  until  sufficiently  dry. 
It  is  then  stopped  in  the  same  manner  as  white  work,  but 
using  stiff  stopping  for  large  holes  and  steel  scrapers  in- 
stead of  wood.  The  stopping  is  made  with  the  same 
kind  of  plaster,  size  water,  and  color  as  was  used  for 
the  ground  color  of  the  marble  that  is  being  imitated. 
The  stopping  and  stoning  is  repeated  as  before,  and  it  is 
finally  polished  with  putty  powder,  using  pUre  linseed  oil 
instead  of  water.  The  repeated  operations  of  stopping 
and  stoning  must  not  be  proceeded  with  until  the 
previous  stopping  is  perfectly  set,  and  the  work  dry.  A 
small  portion  of  spirits  of  turpentine  is  sometimes  added 
to  the  gauged  colored  stuff  to  facilitate  the  drying.  The 
work  between  each  combined  stopping  and  stoning  will 
take  from  one  to  five  days  to  dry,  according  to  the  size 
and  thickness  of  the  work  and  the  state  of  the  atmos- 
phere. Never  dry  the  work  by  heat.  The  thorough  dry- 
ness and  hardness  of  the  work  are  most  essential  be- 
fore proceeding  to  polish  with  the  putty  powder  and  lin- 
seed oil,  because  any  contained  damp  will  work  out  and 
spoil  the  polish.    Work  not  perfectly  dry  may  take  a 


MISCELLANEOUS  MATTERS  277 


high  polish,  but  it  will  soon  go  off  when  the  damp  comes 
through.  Columns  or  large  hollow  work  are  not  so  liable 
to  be  affected  by  the  damp,  as  it  may  escape  through  the 
back;  but  there  must  be  some  opening  or  ventilation  to 
allow  it  to  finally  escape. 

If  the  polishing  is  well  and  carefully  done,  the  polish 
produced  on  scaglioia  will  equal,  if  not  surpass,  that  on 
real  marble.  Tripoli  polishing  stone,  sometimes  called 
alalia,  is  a  kind  of  chalk  of  a  yellowish-grey  color.  Water 
of  Ayr  stone  is  also  used  for  polishing.  In  large  work 
a  rubber  of  felt  dipped  in  putty  powder  may  be  used. 
Salad  oil  is  sometimes  used  for  finishing.  Linseed  oil 
makes  the  hardest  finish,  and  dries  quicker. 

MarezzO'. — Marezzo  artificial  marble  manufactured 
from  plaster  or  Keen's  cement  and  mineral  coloring  mat- 
ter is  made  in  wood  or  plaster  moulds  for  moulded  work, 
and  on  slate  or  glass  benches  if  in  slabs.  If  thick  plate 
glass  is  used,  the  worker  has  the  advantage  of  being  able 
to  look  through  it  to  see  if  the  figure  of  the  work  re- 
quires altering.  Glass  also  has  the  advantage  of  leaving 
a  smoother  and  more  polished  face.  All  wood  and 
plaster  moulds  should  be  got  up  with  a  good  face,  and 
properly  seasoned,  to  save  stoning  and  polishing  the  face 
of  the  work.  Keen 's  cement  may  be  used  advantageous- 
ly in  making  Marezzo,  especially  for  chimney  pieces,  or 
other  works  required  for  exposed  positions.  Keen's 
cement  for  Marezzo  should  be  of  the  highest  class.  If 
the  cement  is  not  of  the  best,  it  will  effloresce,  rendering 
the  work  of  polishing  difficult,  if  not  spoiling  it  alto- 
gether., Keen's  cement  requires  no  size  water,  but  in 
gauging  either  Keen's  or  plaster,  no  more  should  be 
gauged  than  can  be  conveniently  used.  The  quantities 
of  colors.  Keen's  cement,  plaster,  and  size  water  should 
be  measured  and  gauged  pats  kept  for  future  reference. 


278  CEMENTS  AND  CONCRETES 


All  gauge-pots  snould  be  of  earthenware,  as  they  are 
more  easily  cleaned  out,  and  do  not  rust,  as  is  the  case 
with  metal  pots.  All  the  tools  should  be  kept  bright  and 
clean,  as  when  working  scagliola. 

Marezzo  is  made  in  the  reverse  way  to  scagliola,  as  the 
face  or  marble  is  put  in  the  mould  first,  and  the  core  or 
backing  put  on  afterwards. 

All  the  mineral  colors  should  be  of  good  quality,  in 
fine  powder,  and  ground  in  water,  known  as  ' '  pulp. ' '  A 
number  of  basins  should  be  handy,  and  there  should  be 
a  supply  of  twist  silk  in  skeins  varying  in  diameter  from 
%  to  %  of  an  inch,  and  cut  into  lengths  of  14  to  18 
inches.  For  common  work,  good  long  flax  fibre  may  be 
used.  Canvas  is  also  required.  One  end  of  the  silk  or 
fibre  skein  must  be  knotted.  ^  These  are  known  as  ' '  drop 
threads. ' ' 

After  the  moulds  are  made,  seasoned,  and  oiled,  the 
young  hand  may  begin  by  trying  to  make  some  easy 
marble,  for  a  slab  or  chimney-piece.  Gauge  Keen's  extra 
superfine  cement  or  superfine  plaster,  in  a  large  basin 
labelled  No.  1,  well  mixing  it  until  about  the  consistency 
of  cream.  This  is  pure  white.  Now  pour  a  small  quan- 
tity of  this  white  plup  into  two  small  gauge-pots,  Nos. 
3  and  4.  Pour  a  third  of  what  remains  in  the  No.  1 
pot  into  another  gauge  pot.  No.  2.  Take  some  black- 
colored  pulp,  and  make  No.  1  a  blackish-grey.  Color 
in  the  same  way  No  2.  only  very  much  blacker  than 
No.  1.  No.  3  is  now  slightly  tinted  with  pulp  from  No. 
1.  This  leaves  No.  4  pure  white.  Then  take  a  skein  of 
twist  (or  threads),  dip  into  No.  4,  the  pure  white,  and 
well  charge  it  by  stirring  it  about  with  the  fingers ;  take 
out  the  threads,  taking  each  end  between  the  thumb  and 
forefinger  of  each  hand,  and  with  the  remaining  fingers 
of  each  hand  separate  the  threads,  allowing  plenty  of 


MISCELLANEOUS  MATTERS 


279 


*^swag/'  and  strike  this  into  the  face  of  the  mould,  mak- 
ing each  stroke  at  different  angles,  recharging  the 
threads  when  necessary.  Repeat  this  process  with  pulp 
from  No.  3,  but  in  a  lesser  quantity;  then  dip  your 
finger  ends  into  No.  2,  and  fling  drops  about  the  size  of 
large  peas  all  over  the  veining.  These  drops  must  be 
thrown  on  with  considerable  force,  so  as  to  cut  into  the 
veins  as  much  as  possible.  Dip  the  fingers  into  No. 
1,  and  throw  on  No.  2,  using  alternately  from  each  gauge- 
pot  until  you  get  a  uniform  thickness  of  surface  (scag), 
about  %  inch  in  thickness.  Now  run  a  trowel  over  this 
to  lay  down  any  ridges.  Cover  the  work  with  a  piece 
of  canvas,  laying  it  evenly,  smoothly,  and  without 
wrinkles.  Be  careful  to  put  the  canvas  in  the  proper 
place,  as  moving  it  would  spoil  the  lines  of  the  veining; 
then  spread  a  quantity  of  dry  coarse  Keen's  lightly  over 
the  entire  surface.  This  will  absorb  any  superfluous 
moisture  through  the  canvas.  After  the  canvas  and 
coarse  Keen's  have  lain  from  ten  to  tv/enty  minutes,  or 
according  to  the  stiffness  of  the  gauge  of  the  marble,  the 
canvas  and  coarse  cement/  are  easily  lifted  off.  Should 
any  portion  of  the  face  of  the  scag  leave  the  mould,  and 
adhere  to  the  canvas,  it  is  taken  off  and  put  back  in 
its  place  in  the  mould.  The  whole  surface  is  now 
trowelled  to  render  it  dense  and  hard.  The  moisture 
should  be  sufficiently  absorbed,  or  the  trowelling  may 
spoil  the  figure.  The  proper  absorption  of  the  moisture 
by  the  dry  cement  through  the  canvas,  and  well  trowel- 
ling, are  most  essential  to  good  work,  ensuring  hardness 
and  density. 

The  core  or  backing  is  now  made  by  using  the  coarse 
Keen's  previously  used  for  absorbing  the  moisture  from 
the  face,  gauging  it  with  some  fresh  coarse  Keen's  as 
stiff  as  possible.    This  is  laid  on  as  thick  as  required.  If 


280  CEMENTS  AND  CONCRETES 


the  face  of  the  scag  be  very  dry,  spread  a  thin  coarse 
gauged  Keen's,  so  as  to  give  a  perfect  cohesion  between 
the  marble  and  the  backing.  The  flat  surface  of  the 
backing"  should  always  be  ruled  or  floated  straight  with 
a  uniform  thickness,  so  as  to  give  a  true  bed  for  the  cast 
when  it  is  taken  out  of  the  mould,  and,  laid  on  a  bench 
ready  for  stoning,  stopping,  and  polishing.  This  can 
be  done  as  soon  as  it  is  thoroughly  set  and  hard,  and  in 
the  same  manner  as  scagliola. 

Marbles  having;  long  stringy  veins  require  a  different 
method  of  putting  in  the  veins.  Take  the  skeins,  or  - 
^  threads, "  by  the  knot  with  one  hand,  and  thoroughly 
saturate  them  with  the  veining  mixture,  and  run  the 
finger  and  thumb  of  the  other  hand  down  the  threads  ' 
to  clear  them  of  any  excess  of  veining  color  with  which 
they  may  be  charged.  Then  give  the  end  not  knotted  to 
your  partner,  holding  the  knot  in  your  left  hand.  Pull 
the  threads  asunder,  so  as  to  take  the  form  of  the  veins 
of  the  marble  you  are  copying,  then  lay  them  in  the 
mould,  leaving  the  knots  hanging  over  the  edge  of  the 
mould,  or  at  least  visible,  to  facilitate  their  removal 
when  required.  The  threads  should  be  arranged  on  the 
mould  so  as  to  take  the  form  of  the  veining.  The  other 
colored  materials  are  then  thrown  upon  the  thread  veins, 
which  quickly  absorb  the  coloring  matter  from  them; 
care  being  taken  that  the  various  colors  are  thrown  or 
dropped  from  the  finger  tips,  to  form  the  figure  of  the 
body  of  the  marble  that  is  being  copied.  When  the 
mould  is  sufficiently  and  properly  covered  with  the 
marbling,  take  hold  of  the  knots  and  withdraw  the 
threads.  These  should  be  cleaned  by  passing  down  the 
finger  and  thumb  for  future  use,  saving  the  superfluous  - 
stuff  for  filling  up  any  holes  in  the  marbling.  The 
absorption  of  the  use  of  canvas  and  dry  coarse  Keen's, 


MISCELLANEOUS  MATTERS  281 


-and  the  filling  in  of  the  backing  or  core,  is  then 
proceeded  with  as  before  described. 

Granites,  porphyries,  etc.,  are  made  in  a  different 
manner.  For  porphyries  with  white  and  black  specks, 
make  a  slab  of  white  Keen's  about  %  inch  thick,  and 
another  in  black,  the  same  thickness.  When  they  are 
set  and  hard,  chop  them  into  small  pieces,  then  run  them 
through  a  sieve,  having  a  mesh  to  let  through  the  pieces 
of  the  required  size  only.  The  pieces  retained  in  the 
sieve  can  be  broken  and  sieved  again.  The  whole  is 
now  sieved  again  through  a  smaller  mesh,  which  re- 
tains only  the  size  wanted.  The  refuse  can  be  used  for 
small  work  or  backing  up.  AVhen  the  gauged  stuff  for 
the  facing  is  mixed  of  the  required  tint  (a  reddish- 
brown),  damp  the  black  and  white  specks  with  the 
gauged  color  by  means  of  a  trowel  and  rolling,  care 
being  taken  not  to  break  the  edges  and  faces  of  the 
black  and  white  specks.  When  it  is  well  mixed,  lay  it 
onto  the  face  of  the  mould  about  3-16  inch  thick,  press- 
ing it  as  firmly  and  evenly  as  possible.  Then  absorb  the 
moisture  by  means  of  canvas  and  dry  coarse  Keen's, 
trowel  it  well  to  give  density,  and  fill  in  the  backing  or 
core  as  before.  For  Rouge  Royale, "  ^^Verd  Antique," 
&c.,  requiring  large  white  patches  of  irregular  size,  the 
sieving  can  be  dispensed  with.  The  white  pieces  are 
broken  haphazard,  and  pieces  of  alabaster  can  also  be 
inserted  in  these,  and  many  other  marbles,  due  regard 
being  given  to  the  size  and  quantity,  so  as  not  to  produce 
an  unnatural  effect.  The  remainder  of  the  figure  is 
formed  with  the  ^'drop  threads,"  and  the  other  colors 
being  thrown  on. 

From  this  description  of  Marezzo,  the  workman  will 
understand  that  in  the  case  of  marbles  classed  as  ^ ^Brec- 
cias,such  as  ^' Rouge  Royale, "    Black  and  Gold,"  &c., 


282  CEMENTS  AND  CONCRETES 


having  patches  and  rough  jagged  veins  in  them,  he  must 
have  flat  pieces  of  the  required  color  previously  made 
and  broken  up,  or  alabaster,  as  the  case  may  be  inserted 
into  them,  and  the  veining  done  with  the  ''drop  threads'^ 
and  that  fine  or  long  veining  threads  are  not  required; 
that  unicolored  marbles  require  no  veining  threads ;  that 
the  long  veined  marbles  require  the  long  threads,  and  in 
some  cases  the  ''drop  threads''  as  well,  and  that  granites, 
porphyries,  &c.,  require  no  threads;  that  black  is  diffi- 
cult to  make  owing  to  the  pure  white  cement  requiring  so 
much  color;  and  finally,  that  in  all  cases,  whether  Ma- 
rezzo  or  scagliola,  the  polishing  is  done  in  a  similar  man- 
ner, whether  using  plaster. or  Keen's  cement. 

The  details  given  must  be  carefully  followed  to  pro- 
duce work  artistic  in  figure  and  appearance.  The  direc- 
tions for  making  "St.  Ann's"  so  far  as  manipulation  is 
concerned,  apply  to  all  others.  A  little  patience,  prac- 
tice, and  perseverance  will  soon  give  confidence  and  ex- 
pertness  in  producing  sound  scagliola  and  Marezzo. 

Granite  Finish. — Granite  is  a  peculiar  finishing  coat  of 
plaster  which  is  sometimes  used  in  this  country  to  imi- 
tate granite.  For  granite  finish,  first  render  the  walls 
with  hydraulic  lime,  and  when  nearly  dry  lay  with  a  thin 
coat  of  the  same  material  but  colored  light  brown.  Then 
while  this  coat  is  still  moist,  splash  the  surface  lightly 
with  white  stuff,  then  with  black  stuff,  using  only  half 
as  much  as  used  for  the  white  stuff.  The  red  stuff  is 
best  applied  by  dotting  the  surface  with  a  small  brush 
charged  with  the  colored  stuff.  After  these  colored  lime 
stuffs  are  firm,  but  not  set,  the  surface  is  carefully  trow- 
elled, using  the  minimum  of  water  so  as  not  to  mix  the 
various  colored  stuffs.  The  surface  is  sometimes  left  in  a 
rough  state,  or  as  left  when  splashed.   After  the  surface 


MISCELLANEOUS  MATTERS  283 


is  firm,  it  is  set  out  and  jointed  to  represent  blocks  of 
graite. 

Granite  Plastering, — Granite  plastering  is  a  method, 
introduced  by  the  author,  to  imitate  granite.  This  mode 
of  imitating  granite  is  based  on  the  scagliola  process.  It 
is  also  somewhat  similar  to  the  granite  finish,  and  gives 
better  and  more  reliable  results. 

The  method  of  executing  granite  plaster  work  is  as 
follows :  First  select  the  most  suitable  lime  or  cement 
for  the  situation,  such  as  Portland  cement  or  hydraulic 
lime  for  exterior  work,  and  Parian  or  other  white  cement 
for  interior  work.  Having  decided  on  the  material, 
gauge  three  different  colored  batches,  one  white,  one  red, 
and  one  black,  taking  care  that  the  stuff  is  gauged  stiff 
and  expeditiously  so  as  to  obtain  a  hard  substance.  The 
material  is  colored  to  the  desired  shades,  as  described 
for  scagliola  or  colored  stuccos.  When  gauged  the  stuffs 
are  laid  separately  on  a  bench  and  rolled  until  about 
3-16  inch  thick,  and  when  nearly  set  they  are  cut  into 
small  irregular  cubes  and  allowed  to  set  and  harden.  The 
wall  is  then  floated,  ruled  fair,  and  the  surface  keyed, 
and  when  set  it  is  laid  with  a  thin  bedding  coat  of  simi- 
lar stuff  used  for  the  floating,  but  colored  light  brown. 
The  colored  cubes  are  then  mixed  together  in  due  propor- 
tions, and  gauged  with  a  portion  of  the  light  brown  col- 
ored stuff  and  laid  on  the  thin  coat  while  it  is  soft.  The 
whole  is  then  firmly  pressed  with  a  hand-float  until  a 
close,  compact,  and  straight  surface  is  obtained,  taking 
care  when  pressing  the  stuff  not  to  break  the  cubes. 
After  the  stuff  is  set  and  perfectly  dry  and  hard,  the 
surface  is  rubbed  down  and  polished,  as  described  for 
scagliola  or  for  marble  plaster.  The  bedding  coat  should 
be  sufficiently  thick  to  receive  the  colored  cubes,  other- 
wise the  larger  cubes  will  project  at  parts,  and  cause 


284 


CEMENTS  AND  CONCRETES 


extra  labor  in  making  a  uniform  and  straight  surface. 
Unless  the  cubes  are  fairly  level  when  pressed,  the  sur- 
face will  have  a  spotty  appearance,  besides  being  more 
difficult  to  polish.  Where  expense  or  time  is  a  consid- 
eration, a  striking  appearance  is  obtained  at  less  cost 
than  polished  work,  by  simply  finishing  the  surface  with 
a  cross-grained  hand-float,  and  a  semi-polished  surface  is 
obtained  by  trowelling,  or  by  scraping  the  surface  with 
a  joint-rule.  Grey  or  light-colored  granites  are  imitated 
by  altering  the  colors  of  the  cubes  and  the  bedding  coat 
as  desired.  Bold  and  striking  effects  on  wall  surfaces 
can  be  obtained  by  a  combination  of  different  colored 
granites,  laid  out  in  bands  and  borders.  The  effect  can 
be  increased  by  the  introduction  of  borders  in  sgraffito^ 
with  the  bands  in  granite  plaster. 


PART  II 


CEMENTS  AND  CONCEETES,  AND  HOW  TO  USE 

THEM. 

It  is  not  necessary  to  the  workman  that  he  should  ex- 
pend a  long  period  of  his  valnable  time  in  reading  up 
the  history  of  cements  and  concretes,  nevertheless  it  is 
proper  he  should  be  acquainted  with  the  outlines  of  the 
origin,  growth,  and  development  of  cements,  concretes 
and  their  uses,  and  to  this  end  the  following  brief  his- 
torical summary  is  presented,  sufficient  to  give  the  work- 
man a  fair  idea  of  the  beginning  and  growth  of  the  use 
of  cements  and  concretes : 

The  word  concrete  is  of  Latin  origin,  and  signifies  a 
mass  of  materials  bound  or  held  together  by  a  cementing 
matrix.  The  Romans  used  concrete  B.  C.  500.  They 
made  good  use  of  lime  concrete  both  in  the  construction 
of  buildings  and  roadways.  ''Eoads,"  says  Gibbon, 
^'were  the  most  important  element  in  the  civilization 
of  ancient  Rome;  and  the  cost  of  the  Appian  Way  was 
such  as  to  entitle  it  to  the  proud  designation  of  'Re- 
gina  Viarum'  (the  Queen  of  Roads)."  The  Appian 
(the  oldest  of  the  Roman  highways)  was  commenced  by 
Appius  Claudius  Gains,  when  he  was  censor,  about  three 
centuries  before  the  birth  of  Ghrist.  It  extended  from 
Rome  to  Gapua,  whence  it  was  consequently  carried  on 
to  Tarentum  and  Brundusium.  Antonio  Nibby,  an 
archaeologist  of  the  highest  authority,  states  that  the 
Appian  Way  had  an  admirable  substructure,  with  lime 
concrete  materials  superimposed,  and  large  hexagonal 

285 


286  CEMENTS  AND  CONCRETES 


blocks  of  stone  laid  on  the  top  of  all.  The  Eomans  built 
concrete  aqueducts,  often  several  miles  long,  to  convey 
water  to  the  cities.  The  palace  of  Sallust,  the  historian, 
was  built  about  B.  C.  50,  and  was  frequently  used  as  a 
residence  by  most  of  the  emperors  until  as  late  as  the 
fourth  century.  It  was  partly  burnt  by  Alaric  in  the 
year  410.  This  once  magnificent  edifice  was  erected  on 
a  strange  site,  partly  in  the  valley  at  the  foot  of  the 
Quirinal  Hill,  and  partly  on  the  top  of  the  hill.  The 
latter  portion  of  the  palace,  which  was  of  great  extent, 
has  been  almost  wholly  destroyed  by  the  builders  of  the 
modern  boulevard.  The  walls,  which  were  thick  and 
high,  were  most  valuable  examples  of  the  Roman  use  of 
concrete,  unfaced  by  brick  or  stone.  There  is  still  visi- 
ble evidence,  in  the  form  of  impressions  left  on  those 
walls,  which  clearly  demonstrates  their  method  of  cast- 
ing walls  in  situ  by  means  of  wood  framing.  Rows  of 
timber  uprights,  about  10  feet  high,  6  inches  wide,  and 
3  inches  thick,  were  fixed  along  both  faces  of  the  in- 
tended wall.  Boards  about  10  inches  wide  and  II/2 
inches  thick,  in  suitable  lengths,  were  then  nailed  hori- 
zontally along  the  uprights,  thus  forming  two  parallel 
wooden  walls,  into  which  the  concrete  was  laid  and 
rammed  until  the  space  between  the  boards  was  filled 
to  the  top.  When  the  concrete  had  set,  the  wood  fram- 
ing was  removed,  and  refixed  at  the  top  of  the  concrete, 
the  whole  process  being  repeated  until  the  wall  was 
raised  to  the  required  height.  This  concrete  was  far 
more  durable  than  brick  or  stone.  The  jerry-builders  of 
the  modern  Rome  had  no  difficulty  in  pulling  down  the 
stone  wall  of  Servius,  but  the  concrete  walls  required  the 
use  of  dynamite  to  complete  their  destruction.  After 
withstanding  the  wear  and  tear  of  many  centuries,  and 
the  repeated  onslaughts  of  the  Goths  and  Vandals,  it  was 


HOW  TO  USE  THEM 


287 


left  to  the  nineteenth-century  speculative  builder  to  de- 
stroy those  interesting  remains. 

The  use  of  concrete  for  floors  and  roofs  is  of  great  an- 
tiquity. It  was  employed  for  this  purpose  by  the  Ro- 
mans in  the  time  of  Julius  Caesar.  Professor  Middleton, 
in  his  first  book^  Ancient  Eome,"  states  that  the  whole 
of  the  upper  floor  of  the  Antrium  Vesta  is  formed  of  a 
great  slab  of  concrete^  14  inches  thick,  and  about  20  feet 
in  span,  merely  supported  by  its  edges  on  travertine  cor- 
bels, and  having  no  intermediate  supports.  In  his  sec- 
ond book,  ^ '  The  Remains  of  Ancient  Rome, ' '  Professor 
Middleton  mentions  that  the  Romans  used  concrete  for 
the  construction  of  the  Pantheon,  which  was  erected 
about  the  time  of  Christ.  A  curious  and  apparently  un- 
accountable feature  as  regards  practical  purposes  is  that 
the  concrete  is  faced  with  bricks,  which  were  faced  again 
either  with  stucco  or  (in  special  cases)  with  marble 
veneer.  The  Professor  gives  a  sketch  showing  the  ex- 
terior facing  and  the  section  of  a  wall  of  this  kind,  the 
entire  mass  being  composed  of  concrete,  except  a  facing 
of  thin  bricks,  triangular  in  plan,  with  the  points  in- 
wards. As  the  author  observes,  these  bricks  could  not 
possibly  be  intended  as  a  matrix  for  concrete,  as  it  would 
not  have  withstood  the  pressure  of  the  latter  while  in  a 
wet  state.  It  must  therefore  have  been  necessary  to  re- 
tain the  brick  and  the  concrete  with  an  external  tim^ 
ber  framing,  as  in  the  case  of  unfaced  concrete.  There 
could  be  no  gain  of  strength  or  other  benefit  to  compen- 
sate for  the  time  expended  setting  the  brick  skin.  The 
dome  of  the  Pantheon  is  142  feet  in  diameter  and  143 
feet  high.  This  is  also  formed  with  brick- faced  concrete. 
It  has  often  been  described  and  even  drawn  by  various 
authors  as  essentially  a  brick  dome.  Professor  Middle- 
ton  remarks  there  must  have  been  very  elaborate  con- 


288  CEMENTS  AND  CONCRETES 


struction  of  centring  for  this  and  other  massive  concrete 
vaults.  He  states  they  employed  a  method,  which  has 
become  common  of  late,  to  avoid  the  necessity  of  build- 
ing up  the  centring  from  the  ground.  They  set  back 
the  springing  of  the  arch  from  the  face  of  the  pier,  so 
as  to  leave  a  ledge  from  which  the  centring  was  built- 
the  line  of  the  pier  being  afterwards  carried  up  until  it 
met  the  intrados  of  the  arch,  leaving  it  a  segmental  one. 
The  Professor  also  found  signs  of  timber  framing  for 
walls  in  the  remains  of  the  Golden  House  of  Nero,  un- 
der the  Thermae  of  Titus,  where,  he  says,  ''the  chan- 
nels formed  by  the  upright  posts  are  clearly  visible. 
These  upright  grooves  on  the  face  of  the  wall  are  about 
6  inches  wide  by  4  inches  deep,  and  they  are  afterwards 
filled  up  by  the  insertion  of  little  rectangular  bricks,  so 
as  to  make  a  smooth  unbroken  surface  for  the  plaster- 
ing.This  method  is  difficult  to  understand.  Accord- 
ing to  the  present  practice,  the  supports  should  be  fixed 
outside  the  line  of  wall  surface  and  leave  no  space  to 
fill  in  afterwards.  He  also  mentions  a  striking  example 
of  the  tenacity  of  good  concrete  in  the  Thermae  of  Cara- 
calla,  at  a  part  where  a  brick-faced  concrete  wall  origin- 
ally rested  on  a  marble  entablature  supported  by  two 
granite  columns.  ''In  the  sixteenth  century,"  he  says, 
' '  the  columns  and  the  marble  architrave  above  them  w^ere 
removed  for  use  in  other  buildings,  and  yet  the  wall 
above  remains,  hanging  like  a  curtain  from  the  concrete 
wall  overhead. This  proves  that  the  Romans  bestowed 
as  much  thought  and  care  on  the  materials  and  their 
composition  as  they  did  on  their  construction.  Profes- 
sor Middleton  notes  that  the  larger  pieces  of  aggregate  in 
the  concrete,  which  are  not  close  together,  are  so  evenly 
spaced  apart  as  to  lead  to  the  conclusion  that  they  must 
have  been  put  in  by  hand,  piece  by  piece. 


HOW  TO  USE  THEM 


289 


Dr.  Le  Plongeon,  during  his  explorations  in  Peru, 
found  many  remains  of  mud  concrete  walls.  Although, 
they  were  built  many  centuries  ago,  they  have  proved 
sufficiently  durable  to  exist  until  to-day.  The  materials 
were  placed  between  two  rows  of  boards,  and  well  beat- 
en, and  the  exteriors  were  sometimes  decorated  with  plas- 
ter work.  Thus  it  appears  that  the  Peruvian  builders  of 
the  period  of  the  Incas  anticipated  by  centuries  the 
method  (but  not  the  material)  of  our  modern  concrete 
buildings.  Le  Plongeon's  researches  conclusively  estab- 
lish the  fact  that  these  Indians  were  masters  of  concrete 
building  and  plastering.  The  walls  of  the  fortress  of 
Ciudad  Rodrigo  in  Spain  are  built  of  concrete.  There 
are  over  twelve  miles  of  arches  and  tunnels  constructed 
with  concrete  in  the  Varone  Aqueduct,  which  supplies 
Paris  with  water.  One  of  the  arches  over  the  Orleans 
Road,  in  the  Forest  of  Fontainebleau,  has  a  span  of  125 
feet  without  a  joint,  the  arches  and  the  water-pipe  or 
tunnel  being  entirely  composed  of  beton,  made  with 
Portland  cement,  hydraulic  lime,  and  the  sand  found  on 
the  spot.  Concrete  blocks  weighing  over  20  tons  were 
used  in  the  construction  of  the  Suez  Canal,  3,000,000 
tons  of  these  blocks  being  required  at  Port  Said  alone. 
Besides  the  unquestionable  durability  of  concrete,  it  also 
possesses  fire-resisting  and  w^aterproof  powers  of  the 
highest  degree.  Constructional  works  formed  with  con- 
crete carefully  made  and  applied  may  be  considered  ab- 
solutely fire-resisting  and  damp  proof;  in  fact,  in  these 
respects  concrete  has  long  since  passed  the  experimental 
period,  inasmuch  as  numerous  tests,  under  the  most  try- 
ing and  adverse  circumstances,  attest  the  superiority  of 
this  material  for  sanitary  and  durable  work. 

The  best  concrete  in  France  is  that  made  under  Coign- 
et^s  system  of  ''beton  agglomere,''  and  has  been  used 


290 


CEMENTS  AND  CONCRETES 


with  great  success  in  the  construction  of  various  large 
and  important  works.  In  Paris  many  miles  of  the  sew- 
ers have  been  formed  of  this  material,  and  a  church  in 
the  Gothic  style,  from  the  foundations  to  the  top  of  the 
steeple  (which  is  136  feet  high)  is  entirely  formed  of 
beton.  The  work  was  prosecuted  without  cessation  for 
two  years,  and  was  exposed  to  rain  and  frost,  but  has  not 
suffered  in  the  slightest  way  from  the  extremes  of  tem- 
perature. The  strength  of  this  material  for  constructive 
work  may  be  judged  by  the  thickness,  or  rather  want  of 
thickness,  in  the  construction  of  a  house,  six  stories  high, 
^  having  a  Mansard  roof — cellar,  19  inches,  first  story,  15 
inches;  second  story,  13  inches,  and  diminishing  1  inch 
every  successive  story,  so  that  the  sixth  story  was  9 
inches.  The  cellars  have  a  middle  wall  from  back  to 
front,  from  which  spring  flat  arches  having  a  rise  of  one- 
tenth  of  the  span,  the  crown  being  5  inches  thick,  and 
at  the  springing  9  inches,  which  formed  strong  damp- 
proof  and  fireproof  cellars.  There  are  many  houses  in 
Paris,  and  this  country,  constructed  of  this  material.  It 
has  been  used  in  London  in  the  construction  of  sewers, 
&c.  This  concrete  is  composed  of  Portland  cement, 
sand,  and  lime.  Hydraulic  lime  is  used  for  sewers  and 
waterworks,  and  common  lime  for  ordinary  work.  The 
lime  is  used  in  a  powdered  state.  The  whole  of  the  ma- 
terials are  mixed  in  a  dry  state  by  hand,  and  afterwards 
gauged  in  a  specially  made  pug-mill.  The  least  possible 
amount  of  water  is  added  by  means  of  a  fine  jet  while  the 
pug-mill  is  in  motion.  The  mixture  is  then  spread  in 
thin  layers,  and  beaten  by  rammers  formed  of  hardwood. 
The  quantities  for  coarse  work,  where  a  fine  face  is  not 
required,  are :  Portland  cement,  1  part ;  common  lime, 
^2  part ;  gravel,  13  parts ;  coarse  and  fine  sand,  6  parts. 
And  for  sewers :    Portland  cement,  1-5  part ;  hydraulic 


HOW  TO  USE  THEM 


291 


lime,  1  part;  sand,  6  parts.  And  for  external  work  of 
good  quality:  Portland  cement,  1  part;  lime,  1/2  part: 
sand,  7  parts.  The  above  proportions  are  all  by  meas- 
ure. Specimens  of  Coignet  beton  at  two  years  old  have 
attained  a  crushing  strength  of  7,400  lbs.  to  the  square 
inch. 

Fine  Concrete. — ''No  book  on  plastering, "  says  Miller, 
''would  be  complete  without  a  description  of  the  meth- 
ods for  working  'fine  concrete'  (here  termed  'fine  con- 
crete' to  distinguish  it  from  rough  concrete  as  used  for 
foundations,  &c.),  which  is  now  coming  into  general  use 
for  paving  purposes,  staircases,  and  constructive  and 
decorative  works  for  buildings.  Floors,  roofs  and  simi- 
lar works  which  are  finished  with  fine  concrete^  being 
within  the  plasterer's  province,  also  demand  description. 
The  proper  manipulation  of  the  plastic  materials,  which 
is  imperative  for  sound  concrete^  is  undoubtedly  plaster- 
er's work.  The  higher  branches  of  concrete  work,  for 
architectural  construction  and  decoration,  embrace 
model-making,  modelling,  piece-molding  and  casting. 
Concrete  construction  is  therefore  essentially  a  part  and 
parcel  of  the  plasterer's  art  and  craft.  The  construc- 
tion of  concrete  staircases  in  situ  affords  a  striking  ex- 
ample of  the  necessity  of  employing  plasterers.  Only  a 
plasterer  can  manipulate  the  materials  correctly,  make 
the  nosing  mitres  sharp  and  true,  and  set  the  soffits  of 
the  stairs  and  landings,  and  form  a  true  arris  at  the 
stringing,  whereas  the  non-plasterer  leaves  the  work  un- 
even, rough  and  unsound.  The  non-plasterer  can  just 
manage  to  spread  the  stuff  laid  on. the  ground  for  him 
when  laying  paving,  but  he  is  entirely  lost  when  the 
stuff  has  to  be  taken  up  •  on  a  hawk  and  laid  with  a 
trowel  on  an  upright  or  overhead  surface.  He  then  gets 
upset,  or  rather  he  upsets  the  stuff.    The  non-plasterer 


292 


CEMENTS  AND  CONCRETES 


possibly  may  have  been  an  unfinished  apprentice,  or  a 
dunce  at  his  former  trade,  hence  his  trying  another. 
These  remarks  are  not  caused  by  any  hostility  to  other 
trades,  but  are  inspired  by  the  fact  that  many  failures 
in  the  better  class  of  concrete  are  due  to  the  non-plaster- 
er's  incapacity  in  working,  and  his  lack  of  knowledge  of 
the  materials.  Portland  cement  concrete  pavements  were 
first  u^sed  about  sixty  years  ago.  Its  introduction,  im- 
provements, and  subsequent  rapid  strides  for  paving, 
and  in  the  construction  of  staircases,  cast  and  made  in 
situ,  are  due  to  the  plasterers.  Concrete  is  one  of  the 
best  materials  for  paving  the  sidewalks  of  streets,  abat- 
toirs, stables,  breweries,  &c.  It  is  jointless,  impervious, 
non-slippery,  and  can  be  laid  with  a  plain  surface  or 
grooved  to  any  desired  form.  The  only  objection  to 
paving  laid  in  situ  for  streets  is  that  when  it  is  cut  to 
repair  or  alter  gas  or  water  pipes  it  is  difficult  to  make 
it  good  without  the  patches  showing.  This  slight  defect 
can  easily  be  overcome  by  cutting  out  the  whole  bay 
where  the  patches  are,  or  by  forming  a  movable  slab 
over  the  pipes. 

There  has  been  in  recent  years  some  controversy  as 
to  the  department  of  the  building  trades  to  which  lay- 
ing concrete  paving  properly  belongs.  The  claim  is  un- 
doubtedly upheld  in  the  strongest  way  for  the  plaster- 
ers. A  further  argument,  if  one  is  needed,  to  identify 
the  operation  as  a  plasterer's  job,  is  that  the  tools,  skill 
in  which  is  necessary,  are  exclusively  those  of  plaster- 
ers. The  laying  trowel  and  the  hand-float  are  prin- 
cipally used^  and  none  but  plasterers  exclusively  employ 
them,  no  other  workman  in  any  branch  of  the  building 
trades  being  habituated  to  their  use.  In  every  part  of 
the  world  where  <?oncrete  paving  has  been  used  it  has 


HOW  TO  USE  THEM  293 

been  laid  down  by  plasterers,  so  that  it  may  be  looked 
upon  as  their  leg:itimate  sphere  of  work. 

Concrete  is  now  extensively  used  in  preference  to 
earthenware  for  making  sewer  tubes.  Experience  has 
proved  that  the  acids  present  in  liquid  sewage  and  the 
gases  generated  by  the  action  of  a  faecal  decomposition 
do  not  injure  the  concrete  tubes,  but  on  the  contrary  tend 
to  harden  them.  Among  the  many  unlikely  purposes  for 
which  concrete  has  come  into  use  may  be  mentioned  stat- 
uary, vases,  fountains,  sinks,  tanks,  cisterns,  cattle- 
troughs,  silos,  railway  sleepers,  platform  copings,  man- 
telpieces, chimney  pots,  tall  chimneys,  tombs,  tombstones, 
and  coffins.  Concrete  is  slowly  but  surely  coming  to  the 
front  as  one  of  the  most  useful,  economical,  constructive, 
and  decorative  materials  for  works  requiring  strength 
and  endurance.  It  may  now  be  said  to  be  indispensable 
to  the  architect,  engineer  and  builder.  Concrete,  when 
properly  made  with  a  Portland  cement  matrix,  and  slag 
or  a  similar  aggregate,  is  undoubtedly  the  best  fire-proof 
material  used  in  any  building  construction.  It  can  be 
made  thoroughly  waterproof  and  acid  proof,  and  may  be 
moulded  or  carved  to  any  design  and  colored  to  any 
shade.  After  this  brief  historical  review  of  concrete,  the 
practical  considerations  of  the  modern  working  by  plas- 
terers claim  attention.  Before  describing  the  methods 
of  working  the  concrete,  a  description  of  the  materials, 
with  their  characteristics  and  application,  is  given  as  a 
preliminary  guide  and  reference. 

Matrix. — Matrix  is  a  word  used  to  designate  any  ma- 
terial having  a  setting,  binding,  or  cementing  power, 
such  as  limes,  plaster  or  cements.  For  concrete  paving, 
stairs,  floors,  or  cast  work  for  external  purposes,  it  may 
be  truly  said  that  there  is  only  one  matrix,  namely,  Port- 
land cement. 


294  CEMENTS  AND  CONCRETES 


Aggregate. — This  is  a  term  applied  to  those  materials 
held  or  bound  together  by  the  matrix.  Aggregates  may 
be  fibrous  or  non-fibrous,  natural  or  artificial.  The  nat- 
ural aggregates  comprise  granite,  stone,  shells,  marble, 
slate,  gravel,  sand,  metal  filings,  &c. ;  the  artificial  slag, 
brick,  pottery,  scharff,  clinkers,  coke-breeze,  ashes,  glass, 
&c. ;  and  the  fibrous  slag,  wool,  coir,  fibre,  reeds,  hair, 
cork,  tow,  chopped  hay,  straw,  shavings,  &c.  The  fibrous 
aggregates  while  being  principally  of  a  natural  kind,  are 
generally  of  a  vegetable  nature.  They  are  commonly 
used  with  a  plaster  matrix  for  the  interior  works.  The 
best  aggregates  for  the  upper  coat  of  concrete  paving 
are  granite,  slag,  and  some  of  the  hard  limestones.  The 
best  and  cheapest  for  the  first  layer  or  rough  coat  are 
broken  bricks,  old  gas  retorts,  clinkers,  whin  and  other 
stones.  Stone  chippings  from  masons'  yards  and  quar- 
ries are  cheap  and  good.  Shingles  and  gravel  are  also 
used,  but  owing  to  their  round  and  smooth  surfaces  they 
afford  little  or  no  key  for  the  matrix.  When  found  in 
large  quantities  and  at  a  cheap  rate,  they  should  be 
broken  to  render  them  more  angular,  so  as  to  give  a  bet- 
ter key.  Aggregates  are  broken  by  a  crushing  or  stamp- 
ing machine.  In  Paris,  the  stone  aggregates  used  for 
casting  figures,  vases  and  similar  ornamental  works  is 
generally  broken  by  hand. 

Aggregates  should  be  clean,  and  their  surfaces  free 
from  mud  and  dust.  Coarse  aggregates  are  easily 
cleaned  by  turning  on  a  strong  stream  of  water  from  the 
hose.  The  aggregates  should  be  laid  on  an  inclined  plane 
to  allow  the  water  and  dirt  to  run  off.  The  importance 
of  a  clean  aggregate  is  seen  from  the  fact  that  briquettes 
made  from  washed  particles  resist  a  tensile  strain  from 
15  to  20  per  cent,  higher  than  those  made  f-rom  unwashed 
particles,  when  tested  under  similar  conditions. 


HOW  TO  USE  THEM 


295 


Porous  Aggregates. — All  aggregates  of  a  porous  na- 
ture or  having  a  great  suction  should  be  well  wetted 
before  being  gauged,  to  prevent  absorption  of  the  water 
used  for  gauging  the  matrix.  A  porous  aggregate  re- 
quires more  cement  than  one  of  closer  texture,  and  is 
not  as  strong.  Water  has  no  power  to  harden  or  set  an 
aggregate.  It  is  used  to  render  the  mass  plastic,  and  to 
set  the  cement.  No  more  than  is  necessary  for  this  pur- 
pose should  be  used.  Sloppy  cement  will  not  attain  the 
same  degree  of  hardness  as  a  firm  or  stiff  gauged  cement, 
consequently  it  stands  to  reason  that  if  the  water  or  a 
part  of  it  be  absorbed  by  a  porous  aggregate,  it  will  ren- 
der the  matrix,  or  that  part  next  to  the  aggregate,  friable 
and  worthless.  This  may  be  proved  by  gauging  a  part 
of  neat  cement  and  spreading  it  on  a  brick  and  another 
part  on  a  slate.  It  will  be  found  that  the  latter  will  set 
and  become  hard,  whilst  the  former  will  either  crumble 
before  setting,  or  partly  set,  without  getting  hard.  All 
aggregates  are  more  or  less  absorbent,  but  while  the  por- 
ous kinds  will  absorb  the  water  from  the  matrix,  not 
only  leaving  the  portions  in  immediate  contact  with  the 
aggregate  inert,  but  also  weakening  the  whole  body  of 
the  concrete,  the  non-porous  have  little  or  no  absorption, 
water  being  retained  in  the  matrix,  or  a  portion  may  lie 
on  the  surface  of  each  particle  of  aggregate,  thus  tend- 
ing to  harden  the  matrix  and  increase  the  general 
strength  of  the  concrete.  It  may  be  thought  that  these 
defects  are  trivial,  and  can  be  overcome  by  thoroughly 
saturating  the  porous  aggregate  to  prevent  suction,  but 
the  fact  still  remains  that  after  this  or  other  excess  water 
has  dried  out,  the  body  of  the  concrete  must  still  be  por- 
ous, and  this  is  one,  if  not  the  principal  reason,  why 
some  concretes  are  not  damp-proof.  The  quantity  of 
matrix  used  for  ordinary  concrete  being  very  much  less 


296 


CEMENTS  AND  CONCRETES 


than  the  quantity  of  aggregate,  and  the  matrix  not  being 
of  sufficient  thickness  to  resist  the  force  of  atmospheric 
moisture,  the  damp  finds  a  ready  passage  through  the 
porous  portions.  A  mass  of  porous  aggregate  will  ab- 
sorb external  moisture,  and  this  will  gradually  work 
through  the  body  to  the  weakest  or  driest  surface,  or  be 
retained  for  a  time,  according  to  the  state  of  the  atmos- 
phere. The  extra  keying  power  claimed  for  a  porous 
aggregate  is  infinitesimal.  It  may  be  said  not  only  to  be 
of  no  value,  but  unnecessary,  bearing  in  mind  that  in 
well-made  concrete  every  particle  of  aggregate  is  envel- 
oped with  matrix. 

Another  point  to  be  considered  is  the  great  tenacity  of 
Portland  cement  to  most  clean  surfaces,  however  smooth. 
Many  men  will  have  noticed  how  it  clings  and  adheres 
when  set  to  iron,  even  to  the  smooth  blades  of  trowels 
and  shovels.  The  ultimate  tenacity  of  neat  Portland 
cement  after  being  gauged  twelve  months  is  about  500 
lbs.  per  square  inch. 

Compound  Aggregates. — The  proper  selection  and  use 
of  aggregates  for  a  true  concrete  is  not  secondary,  but 
of  equal  importance  to  the  matrix.  As  inferior  aggre- 
gates are  in  the  majority,  it  is  advisable  to  take  their  de- 
fects into  consideration.  For  concrete  floors,  roofs,  and 
stairs,  where  strength,  durability,  and  fire  resisting  prop- 
erites  are  imperative,  gravel  and  coke-breeze  as  aggre- 
gates stand  lowest  in  the  scale.  Owing  to  their  abun- 
dance and  cheapness,  however,  or  for  want  of  better  ma- 
terials, their  use  is  often  unavoidable.  Their  individual 
defects  may  be  partly  if  not  wholly  corrected  by  a  com- 
bination of  two  or  more  aggregates  so  as  to  balance  their 
respective  good  and  bad  qualities.  It  is  self-evident  that 
the  hard,  non-porous,  and  incombustible  nature  of  gravel 
will  correct  the  soft,  porous,  and  combustible  nature  of 


HOW  TO  USE  THEM 


297 


coke-  breeze,  and  that  the  light,  rough,  angular,  and  elas- 
tic nature  and  variety  of  size  of  coke-breeze  will  counter- 
balance the  disadvantages  of  the  heavy,  smooth,  round, 
and  rigid  nature  and  uniformity  of  size  of  gravel.  The 
strength,  irregularity  of  size,  and  form  of  broken  bricks 
and  its  incombustible  nature,  causes  it  to  be  a  direct  gain 
to  either  of  the  above.  The  mixing  of  various  aggre- 
gates may  seem  of  small  importance,  but  if  by  their  judi- 
cious amalgamation  the  strength  is  enhanced,  or  the 
weight  or  cost  of  the  material  decreased,  or  gained,  if  the 
practice  enables  any  waste  or  by-product  to  be  utilized, 
then  the  advantage  becomes  obvious.  To  argue  by 
analogy,  it  is  well  known  that  it  is  by  the  judicious  com- 
bination and  manipulation  of  various  materials  that 
mortars  and  cements  attain  their  strength  and  hardness, 
therefore  the  same  course  will  give  equally  good'  results 
with  concretes,  while  rendering  economy  with  safety  pos- 
sible. 

The  compressive  and  tensile  strength  of  concrete  is 
influenced  both  by  the  matrix  and  the  aggregate.  Aggre- 
gates which  are  uniform  in  size  (or  if  of  various  sizes 
which  are  not  graduated  in  proportion  to  each  other),  or 
having  their  surfaces  spherical,  soft  or  dirty,  will  not 
bind  with  the  matrix,  or  key  or  bend  with  each  other,  so 
well  as  those  which  are  of  various  graduating  propor- 
tional sizes,  and  have  their  surfaces  hard,  angular  and 
clean. 

Sand  and  Cement. — Sand  is  extensively  used  as  an 
aggregate  in  Portland  cement  for  cast  work,  mouldings, 
and  wall  plastering.  Fine  sand  does  not  give  so  good 
results  for  strength  as  coarse  sand,  and  a  hard-grained 
sand  is  more  durable  than  a  soft  one.  Ground  brick- 
bats or  pottery,  sandstone  and  flints,  fine  gravel,  smithy 


298  CEMENTS  AND  CONCRETES 


ashes,  and  coke-breeze  are  often  used  as  substitutes  for 
sand. 

It  has  generally  been  assumed  that  sharp  coarse  sand 
is  one  of  the  best  and  strongest  for  gauging  with  cement, 
but,  according  to  experiments  made  by  Mr.  Grant,  clean 
sharp  pit  sand  gives  better  results,  as  he  found  that 
whereas  test  briquettes  having  a  sectional  area  of  2i/^ 
superficial  inches,  composed  of  equal  proportions  of 
coarse  sand,  broke  at  the  end  of  twelve  months  with  a 
tensile  strain  of  724  lbs.,  it  required  815  lbs.  to  break 
briquettes  composed  of  equal  parts  of  cement  and  pit 
sand.  With  reference  to  various  sands  suitable  for  mak- 
ing mortar  with  cement,  Mr.  Grant's  experiment  is  of  a 
most  surprising  nature,  as  it  indicates  that  sand  made 
from  ground  clay  ballast,  or  ground  brick — which  are 
identical — and  Portland  stone  dust,  were  superior  to  pit 
or  sea  sand,  or  smiths'  ashes. 

The  following  shows  the  results  of  tests  of  various 
aggregates  made  by  Lieutenant  Innes.  The  briquettes 
are  composed  of  Portland  cement,  sand,  or  other  aggre- 
gates, in  the  proportions  of  1  to  2,  and  were  kept  in 
water  for  seven  days. 

It  will  be  seen  that  Portland  stone  dust  gave  the  best 
results,  and  the  others  follow  in  this  order — coarse  sea 
sand,  rough  pit  sand,  smooth  pit  sand,  drifted  sea  sand, 
and  lastly  smithy  ashes.  If  the  dust  had  been  elimi- 
nated, the  tests  would  be  more  valuable.  The  degree  of 
coarseness  has  a  considerable  influence  on  the  strength 
of  the  concrete  and  mortar.  Fire  sand  makes  weaker 
mortar  than  coarse.  The  following  table  gives  the  re- 
sults of  two  series  of  tests  carried  out  by  Mr.  Grant. 
The  cement  was  sifted  through  a  sieve  with  2,580  meshes 
to  the  square  inch,  and  was  made  into  briquettes  with  2 


HOW  TO  USE  THEM 


299 


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300  CEMENTS  AND  CONCRETES 

parts  of  sand  by  weight.  All  the  briquettes  are  kept  in 
water. 


Tensile  Tests  of  Portland  Cement  and  Sand  (Coarse 
AND  Fine)  . 


No. 

Sand 
tested 

by 
Sieves. 

At  28 
days. 

60 
days. 

91 
days. 

182 
days. 

273 
days. 

364 
days. 

First  Series— 

Nos. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

lbs. 

1 

1  cement  to  3  sand. 

20-30 

78.5 

113.9 

116.9 

142.3 

178. 

205.5 

2 

ditto. 

Second  Series— 

10-20 

137.1 

239.5 

223. 

231.5 

254.5 

251.5 

3 

1  cement  to  3  sand. 

20-30 

117.2 

134.5 

145. 

156. 

157.8 

213. 

4 

ditto. 

10-20 

212. 

236.5 

206. 

253. 

267.5 

273.5 

In  the  above  each  figure  is  the  average  of  ten  tests, 
the  result  being  given  in  pounds  per  square  inch.  The 
sand  used  in  tests  1  and  3  passed  a  sieve  with  400  meshes 
to  the  square  inch,  and  the  sand  used  in  the  tests  2  and 
4,  through  a  sieve  with  100  meshes  to  the  square  inch. 

Fireproof  Aggregates. — The  selection  of  the  best 
known  fire-resisting  aggregate  for  fire-proof  concrete 
construction  is  of  vital  importance.  Granite,  stone,  and 
flints  splinter  and  crack  when  subjected  to  great  heat, 
or  to  the  sudden  reaction  caused  by  cold  water  used  for 
extinguishing  fires.  Coke-breeze  concrete,  when  under 
the  influence  of  intense  heat,  as  for  example  in  the  midst 
of  a  building  on  fire  (stated  by  Captain  Shaw  to  be 
from  2000  degrees  to  3000  degrees  Fahr.),  will  gradually 
calcine  and  crack,  and  finally  fall  to  dust. 

Slag  is  one  of  the  best  fire-proof  aggregates.  It  is  a 
well-worn  axiom  that  ^^what  has  passed  through  the  fire 


HOW  TO  USE  THEM 


301 


will  stand  the  fire. ' '  There  is  no  other  material  that  has 
passed  the  ordeal  of  fire  like  slag.  Its  great  hardness, 
density,  and  angularity  (when  crushed)  all  tend  to  make 
it  one  of  the  best  substances  for  fire-proof  construction. 
Slag  is  cheap  and  abundant,  but  requires  great  care  in 
selection,  as  some  kinds  contain  a  large  amount  of  sul- 
phur, which  is  very  detrimental  to  Portland  cement, 
causing  the  concrete  to  blow  and  expand.  The  presence 
of  sulphur  can  often  be  detected  by  the  smell  alone. 
When  sulphur  is  present  in  a  heap  that  has  lain  for 
some  time,  or  sufficiently  long  to  allow  the  atmosphere  to 
cleanse  the  outer  surface,  it  is  more  difficult  to  detect.  A 
hole  should  then  be  dug  in  the  heap,  and  the  presence 
of  sulphur  can  be  ascertained  by  smell,  heat,  and  color. 
It  will  smell  strong,  and  if  new  will  be  warm,  and  show 
yellow  patches.  The  power  of  the  sulphur  is  so  great 
that  washing  the  slag  once  will  not  entirely  cleanse  it. 
In  some  cases  frequent  washings  and  long  exposures  to 
the  air  are  necessary.  There  are  some  slags  that  are  free 
or  nearly  so  from  sulphur,  and  which  can  be  had  direct 
from  the  iron  furnaces.  The  slag  from  coal  and  iron 
furnaces  is  largely  employed  for  concrete  paving.  It  is 
hard  and  practically  free  from  sulphur.  The  best  size 
is  %  inch  screenings.  This  when  sifted  yields  a  fine  kind 
for  topping,  and  the  residue  is  useful  for  the  rough  coat. 

The  next  best  fire-resisting  aggregates  are  fine-bricks, 
pottery,  scharff,  hard  clinkers,  and  pumice-stone.  The 
last  has  the  advantage  of  being  extremely  light,  but  it  is 
too  soft  for  the  frictional  wear.  Coke-breeze  may  to  a 
certain  extent  be  deprived  of  its  combustible  nature  and 
rendered  more  fire-resisting  by  washing  and  passing  it 
tlirougrh  a  1/4  i^ich  sieve,  then  adding  1  part  flowers  of 
^'ulphur  and  10  parts  fine  broken  bricks  to  20  parts  of 
^oke-breeze.    The  larger  breeze  rejected  by  the  sieve  can 


302  CEMENTS  AND  CONCRETES 


be  broken  small,  or  used  for  internal  layers  of  concrete. 
The  bricks  should  also  be  passed  through  a  inch  sieve. 
The  finer  the  breeze  and  brick^  the  better  for  receiving 
and  retaining  nails. 

Voids  in  Aggregates. — The  quantity  of  voids  or  in- 
terstices depends  on  the  shape  and  size  of  the  aggregates. 
The  least  quantity  of  voids  will  be  found  in  those  aggre- 
gates which  are  broken  small,  and  contain  pieces  of  va- 
rious sizes.  Gravel  free  from  sand  contains  about  30 
per  cent,  of  voids,  and  broken  stone  of  uniform  size  about 
50  per  cent.  Sand  is  often  mixed  with  gravel,  stones, 
&c.,  to  lessen  the  quantity,  or  fill  the  voids,  so  as  to  en- 
sure the  full  strength  of  the  concrete,  without  adding 
more  cement  than  the  proper  ratio.  The  following 
method  is  used  to  ascertain  the  voids  in  aggregates: — 
Fill  a  box  of  known  capacity  with  damp,  broken  aggre- 
gate ;  start  shaking  it  during  the  operation ;  then  fill  the 
box  to  the  brim  with  water ;  the  quantity  of  water  is  the 
measure  of  the  voids  in  the  aggregate.  Having  now 
briefly  reviewed  the  characteristics  of  the  aggregates 
most  used,  the  practical  conclusions  to  be  drawn  are  that 
they  should  be  angular  in  form,  hard  in  nature,  grad- 
uated in  size,  and  clean. 

Crushing  Strength  of  Concrete. — The  crushing 
strength  of  concrete  depends  upon  the  ratio  of  cement, 
and  the  nature  of  the  aggregate.  Another  important 
factor  is  compression,  done  by  heating  and  ramming. 
Compression  increases  the  weight  of  concrete  about  4  per 
cent.,  and  the  strength  about  25  per  cent.  The  follow- 
ing table  shows  the  crushing  strength  of  concrete  made 
with  Portland  cement  and  various  kinds  of  aggregates  as 
given  by  Mr.  Grant.  The  tests  were  made  with  6-inch 
cubes.  One-half  were  compressed  by  heating  the  con- 
crete into  the  mould  with  a  mallet  ]  the  other  half  were 


HOW  TO  USE  THEM 


303 


not  compressed.  The  whole  were  kept  in  the  air  for  a 
year  before  being  crushed. 

The  granite  and  slag  might  have  been  expected  to 
have  given  the  better  results.  It  is  probable  that  they 
were  unwashed^  and  contained  a  considerable  amount  of 
dust.  If  the  compression  was  done  by  hydraulic  power, 
so  as  to  obtain  a  uniform  compression  in  all  the  cubes, 
the  results  would  be  more  reliable. 


Crushing  Strength  (in  Tons  per  Square  Foot)  op 
Portland  Cement  Concretes  Having  Various 
Aggregates. 


Nature  of  Ag- 
gregate. 

Six  to  One. 

Eight  to  One. 

Ten  to  One. 

Com- 
pressed. 

Not 
Com- 
pressed. 

Com- 
pressed. 

Not 
Com- 
pressed. 

Com- 
pressed. 

Not 
Com- 
pressed. 

Ballast  

81.6 

72.8 

54. 

50. 

42. 

32. 

Portland  stone 

162.4 

120. 

132. 

98. 

88. 

76, 

Granite  

122. 

98. 

78.4 

58. 

62. 

46. 

Pottery  

115.2 

98.4 

88. 

72. 

74. 

56. 

Slag  

92. 

80. 

78. 

56. 

42. 

34. 

Flints  

82. 

62. 

70. 

56. 

60. 

51.2 

Water  for  Concrete. — Water  for  concrete  should  be 
perfectly  clean,  and  free  from  organic  and  inorganic 
impurities.  As  regards  the  quantity,  it  can  only  be 
said  that  for  such  purposes  as  the  foundations  for  pav- 
ing, casting  blocks,  &c.,  or  where  the  material  can  be 
well  rammed,  so  as  to  insure  perfect  consolidation,  less  is 
required  than  where  the  concrete  can  only  be  poured  or 
laid  in  position.  When  mixed  with  sufficient  water,  the 
concrete  occupies  about  one-eighth  more  space  than  when 


304  CEMENTS  AND  CONCRETES 


mixed  with  the  full  quantity,  and  percolation  through 
the  former  gauge  would  be  greater  than  through  the  lat- 
ter. Yet  by  thorough  ramming  the  former  would  oc- 
cupy less  space  and  offer  greater  resistance  to  moisture. 
An  over-watered  gauge  is  slow  to  set,  difficult  to  work, 
liable  to  surface  cracks,  and  often  there  is  a  loss  of 
strength,  caused  by  escape  of  a  portion  of  liquid  cement. 
The  work  will  also  be  unequal  in  strength,  owing  to  the 
liquid  cement  flowing  to  various  or  lov/er  parts,  leaving 
parts  of  the  aggregate  bare  and  weak. 

It  must  not  be  inferred  from  the  foregoing  remarks 
that  water  is  entirely  unnecessary  or  of  little  value  for 
concrete.  On  the  contrary,  it  is  of  the  utmost  value. 
The  evil  is  in  the  abuse,  not  in  the  use.  Portland  ce- 
ment has  a  great  affinity  for  moisture.  For  instance,  if 
a  sack  of  cement  is  left  on  or  in  a  damp  place,  a  part  of 
the  contents  soon  becomes  set  and  extremely  hard,  which 
is  a  proof  of  its  affinity,  and  that  moisture  alone  will 
set  cement  without  water,  far  less  excess  of  water.  Fresh 
cement  requires  more  water  than  stale  cement.  Cement 
gauged  with  sea  water  sets  more  slowly  than  with  fresh 
water.  Sea  water  should  not  be  used  in  concrete  in- 
tended for  paving  stables,  chemical  tanks,  or  similar 
places  where  it  will  come  in  contact  with  ammonia.  Sea 
water  having  a  lower  freezing-point  than  fresh  water,  is 
sometimes  used  in  frosty  weather  to  allow  the  work  to  be 
carried  on.  It  ought  not,  however,  to  be  used  for  ex- 
ternal work,  especially  for  plastering  facade  as  it  has 
the  property  of  attracting  moisture  and  causing  an  ef- 
florescence on  the  surface.  Sometimes  in  frosty  weather 
hot  water,  also  hot  lime,  is  used  for  concrete;  but  al- 
though these  hasten  the  setting  and  hardening  of  con- 
crete, they  also  wash  away  some  of  the  finest  and  best 
particles  of  the  cement  during  the  gauging.    A  part  of 


HOW  TO  USE  THEM 


305 


the  water  ako  forms  in  little  globules  throughout  the 
mass,  and  when  the  water-drops  evaporate  a  series  of 
small  holes  or  bulbs  are  left,  which  deteriorate  the 
strength  of  the  concrete.  Finally,  it  may  be  stated  that 
the  quantity  of  water  required  for  gauging  concrete  is 
regulated  by  the  class  and  condition  of  the  aggregate,  by 
the  state  of  the  atmosphere,  and  by  the  purpose  for 
which  the  concrete  is  required.  Another  important  point 
is  the  careful  and  thorough  incorporation  of  all  the  ma- 
terials when  gauging.  A  mass  of  raw  materials,  if 
gauged  carelessly,  will  require  more  water  to  attain  the 
same  plasticity  than  that  which  is  carefully  gauged.  Ap- 
proximate quantities  of  water  are  given  for  Portland 
cement  plastering.  For  concrete  the  quantity  is  about 
21  gallons  of  water  to  1  cubic  yard  of  dry  materials,  or 
about  1  part  by  volume  to  8  parts.  It  is  a  good  maxim 
to  bear  in  mind  when  mixing  water  for  concrete,  that 
other  things  being  equal,  the  minimum  is  better  than  the 
maximum.  Water  may  be  said  to  give  birth  to  the 
strength  of  cement;  to  carry  the  simile  further,  the  ag- 
gregate may  be  termed  the  bone,  the  matrix  the  skin  and 
sinew,  and  the  water  the  blood  of  concrete. 

Gauging  Concrete. — It  is  a  common  idea  that  concrete 
can  be  gauged  and  used  anyhow,  with  any  aggregate,  or 
with  any  amount  of  water ;  and  in  consequence  of  a  lax- 
ity in  supervision  in  the  selection  of  the  materials,  and 
their  correct  gauging  and  manipulation,  unsatisfactory 
results  are  sometimes  arrived  at,  the  blame  being  at- 
tributed to  the  wrong  cause.  Gauging  concrete  re- 
quires considerable  care  to  avoid  waste  of  the  materials 
and  obtain  the  best  possible  work.  Concrete  can  be 
gauged  either  by  hand  or  by  machinery.  For  small 
quantities,  such  as  for  stairs  and  similar  work,  the 
former  is  almost  invariably  used;  and  tor  large  quan- 


306 


CEMENTS  AND  CONCRETES 


tities,  such  as  for  foundations  or  buildings,  &c.,  the  lat- 
ter, being"  more  economical,  is  preferable.  A  careful 
and  uniform  method  should  be  employed  •  for  hard 
gauging;  nothing  should  be  left  to  chance  or  rule  of 
thumb.  The  gauge-board  should  be  sufficiently  large  to 
allow  the  materials  to  be  turned  over  without  spilling,  it 
should  be  placed  as  near  the  work  as  possible,  and  it 
should  be  cleaned  after  each  gauge. 

For  fine  concrete,  no  more  than  1  cubic  yard  should  be 
gauged  at  a  time.  This  is  as  much  as  three  men  can 
properly  gauge  at  once  and  in  the  proper  time — that  is, 
before  the  initial  sef  begins.  Portland  cement  con- 
crete, unlike  some  mortars,  does  not  improve  by  pro- 
longed working.  If  larger  quantities  are  desirable,  then 
more  men  must  be  employed  in  the  gauging.  All  ma- 
terials should  be  measured  for  each  gauge,  to  ensure  uni- 
form setting  and  strength,  and  also  the  best  work.  This, 
combined  with  the  saving  of  time  and  materials,  will  re- 
pay a  hundredfold  the  cost  of  the  measures.  It  is  a 
common  yet  a  wrong  way,  when  gauging  for  paving  pur- 
poses, to  measure  the  aggregate  by  so  many  barrowfuls 
to  a  sack  of  cement.  Neither  the  aggregate  nor  the  ce- 
ment can  be  accurately  measured  in  this  haphazard  way. 
No  man  fills  a  barrow  twice  alike,  and  the  cement  being 
turned  out  of  the  sacks  direct  onto  the  aggregate  is  apt 
to  vary,  as  it  may  contain  lumps  caused  by  damp,  and 
very  often  some  of  the  finest  cement  is  retained  in  the 
sack,  as  more  often  than  not  it  is  simply  drawn  up  and 
then  thrown  on  one  side  without  shaking  it,  as  would  be, 
or  at  least  should  be  done  if  the  cement  was  emptied  for 
air-shaking.  The  aggregate  should  be  measured  in  a 
bottomless  box  or  frame  with  handles  at  the  ends,  the 
cement  in  a  box  (with  a  bottom),  and  the  water  in  a 
gallon  metal  measure  or  a  pail  made  to  contain  4  gal- 


HOW  TO  USE  THEM 


307 


Ions.  Five  pailfuls  of  this  size  are  about  sufficient  to 
gauge  1  cubic  yard  where  the  concrete  can  be  well 
rammed  or  punned.  For  work  that  is  simply  laid,  1  gal- 
lon extra  is  required.  The  box  frame  is  laid  on  the 
gauge-board  and  filled  with  aggregate  (in  a  damp  state). 
The  frame  is  lifted  off,  and  the  aggregate  spread  over  the 
board  until  about  6  or  7  inches  thick.  The  cement  is 
then  distributed  over  the  aggregate.  The  materials  are 
then  gauged  by  three  men,  two  with  shovels,  and  one 
with  a  rake  or  larry,  the  former  facing  the  latter.  The 
dry  materials  should  be  carefully  but  energetically 
turned  over  twice  or  even  thrice,  and  then  when  being 
turned  over  the  third  time  water  must  be  gradually  ad- 
ded by  means  of  a  rose  fixed  on  a  water-can.  Water 
poured  from  a  pail  is  apt  to  wash  parts  of  the  cement 
away;  the  water  also  cannot  be  regularly  and  gradually 
distributed  over  the  dry  materials  as  when  a  rose  is 
used.  The  mass  is  again  turned  over  twice  or  even 
thrice,  until  thoroughly  incorporated.  This  turning  over 
does  not  consist  of  merely  turning  the  mass  over  in  the 
centre  or  on  one  place  of  the  board,  but  to  be  effectively 
done  a  shoveller  should  stand  at  each  side  of  the  board, 
and  the  raker  at  the  end  to  which  the  mass  is  to  be  first 
turned ;  the  shovellers  lift  the  stuff  and  spread  or  rather 
scatter  it  on  one  end  of  the  board  with  a  jerking  mo- 
tion, and  the  raker  further  mixes  the  stuff  by  working 
each  shovelful  backwards  and  forwards.  This  is  repeat- 
ed, the  stuff  being  turned  to  the  other  end  of  the  board, 
after  which  it  is  turned  to  the  center,  the  water  being 
added  as  already  described.  The  wet  mass  is  then  turned 
over  twice  in  a  similar  manner,  and  finally  finished  in 
the  centre  of  the  board.  The  shovellers  in  the  final  mix- 
ing turn  the  stuff  from  the  outside  of  the  heap  to  the 
centre,  while  the  raker  gives  the  final  touches.  After 


308  CEMENTS  AND  CONCRETES 


being  gauged,  it  should  not  be  disturbed,  but  immediate- 
ly shovelled  into  pails,  and  conveyed  to  the  place  of  its 
use.  The  ^ '  initial  set ' '  begins  nearly  or  as  soon  as  gauged, 
and  any  after  or  unnecessary  disturbance  tends  to  de- 
stroy the  setting  properties  of  the  cement.  The  practice 
of  gauging,  and  afterwards  regauging  or  knocking  it  up, 
is  most  objectionable,  as  it  destroys  its  setting  properties. 
No  more  should  be  gauged  at  one  time  than  can  be  con- 
veniently laid  in  one  operation.  The  gauging  of  this 
valuable  material  should  not  be  left  entirely  to  unskilled 
labor,  but  ought  to  be  carried  out  under  careful  super- 
vision. 

Ramming  Concrete. — The  ramming,  beating,  or  pun- 
ning of  concrete  is  of  great  importance.  It  compresses 
the  concrete,  rendering  it  more  dense  and  free  from 
voids,  and  forces  out  all  superfluous  water.  The  re- 
sultant gain  in  strength,  durability,  and  imperviousness 
is  by  no  means  to  be  despised.  Without  compression  it 
is  impossible  to  obtain  impervious  concrete.  Prolonged 
ramming,  however,  is  dangerous,  as  it  may  be  contin- 
ued until  the  cement  is  set^  which  would  be  a  direct  loss 
of  strength.  For  this  reason,  the  ramming  of  concrete 
made  with  quick-setting  cement  should  immediately  fol- 
low the  deposition  of  the  material,  and  be  expeditiously 
done.  The  concrete  should  always  be  gauged  rather 
stiff  than  soft.  If  in  the  latter  form,  the  ramming  will 
separate  the  more  fluid  portions,  and  produce  strata  of 
different  densities.  When  the  concrete  is  deposited  in 
layers,  the  joints  of  each  layer,  if  dry  or  exposed,  should 
be  well  swept  and  watered  before  the  next  layer  is  de- 
posited. It  is  often  advisable,  especially  in  very  dry 
work,  to  brush  the  joints  with  liquid  cement  after  they 
have  been  swept  and  wetted.  For  larger  constructional 
work,  the  joints  should  also  be  keyed  by  aid  of  a  pick,  or 


HOW  TO  USE  THEM 


m 


by  inserting  stones  at  intervals  into  the  concrete  before 
it  is  set^  leaving  them  projecting  3  or  4  inches  above  the 
level  of  the  joint.  Another  method  of  forming  a  key  is 
effected  by  forcing  a  batten  on  edge  about  2  or  3  inches 
deep  into  the  concrete,  at  the  middle  of  the  joint,  and 
when  the  concrete  is  firm  or  nearly  set  the  batten  is  ex- 
tracted, thus  leaving  a  groove  which  forms  a  key  for  the 
succeeding  layer. 

No  layer  that  has  to  be  left  for  some  time,  or  until 
dry,  should  be  less  than  4  inches  deep.  Thin  layers  are 
always  a  source  of  weakness.  If  the  successive  layers 
can  be  laid  before  the  previous  one  is  firm  or  set,  the 
thickness  is  not  of  so  much  consequence.  For  large 
work,  when  each  layer  has  to  stand  until  set,  the  thick- 
ness may  vary  from  9  to  12  or  even  18  inches.  Eam- 
ming  may  be  done  by  using  an  iron  punner,  or  one  made 
of  hardwood  and  bound  with  iron.  Wooden  mallets 
and  punchers  or  iron  hand-floats  are  most  suitable  for 
ramming  stairs  and  cast  work.  The  gain  in  strength 
is  shown  in  the  table  of  the  crushing  strength  of  Port- 
land cement  concrete. 

Thickness  of  Concrete  Paving. — The  thickness  of  con- 
crete paving  laid  in  situ  is  regulated  according  to  the 
purpose  and  the  position  of  the  work.  The  thickness  al- 
so depends  upon  the  nature  and  solidity  of  the  founda- 
tions. It  is  obvious  that  a  thicker  paving  is  required 
for  a  foundation  that  is  weak  or  soft  than  for  one  that 
is  strong  and  hard.  The  best  foundations  are  those  com- 
posed of  strong  and  well-laid  rough  concrete.  Founda- 
tions composed  of  broken  bricks  or  stone  thoroughly  con- 
solidated by  ramming  are  the  next  best.  The  thickness 
of  foundations  is  also  regulated  by  the  nature  of  the 
soil  and  the  subsequent  traffic.  Paving  the  sidewalks 
of  mam  streets,  or  where  the  traffic  is  heavy  and  con- 


310  CEMENTS  AND  CONCRETES 


tinuous,  should  not  be  less  than  2  inches.  For  a  medium 
traffic,  and  on  a  strong  foundation,  a  thickness  of  1^^ 
inches  will  be  sufficient.  For  side  streets,  garden  paths, 
passages  in  houses,  or  similar  places  where  the  traffic  is 
light  and  limited,  a  thickness  from  1  to  l^/^  inches  will 
be  ample  if  on  a  rough  concrete  foundation ;  but  if  on  a 
dry  ' '  dry, ' '  that  is,  broken  brick  or  stone  one^  the  thick- 
ness should  not  be  less  than  II/2  inches.  The  thickness 
for  stable  floors  may  vary  from  3  to  4  inches,  according 
to  the  class  of  horses.  For  instance,  a  thickness  of  3 
inches  would  be  ample  for  race  or  carriage  horses,  but  4 
inches  is  necessary  for  heavy  cart  horses.  The  same 
rule  applies  to  yards,  a  thickness  of  3  or  3^/^  inches 
being  sufficient  for  carriages,  while  4  inches  is  required 
for  carts,  wagons,  &c.  Factory  floors  are  generally  made 
2  inches  thick,  but  where  there  is  machinery  or  wheel 
traffic  a  thickness  from  2^  to  3  inches  is  employed.  By 
computing  the  volume  and  nature  of  the  traffic,  and 
comparing  the  tests  of  concrete  paving  given  herein,  the 
requisite  thickness  will  be  readily  obtained.  It  must  of 
necessity  greatly  depend  on  the  class  of  the  materials 
and  manipulation  used  for  the  paving.  Like  most  other 
articles,  a  good  material  will  go  further  and  last  longer 
than  a  bad  one. 

Concrete  Paving, — Good  pavements  proclaim  a  city's 
progress.  Isodorus  states  that  the  Carthaginians  were 
the  first  people  to  pave  streets.  The  subject  of  paving 
and  floors  will  be  best  understood  by  dividing  it  into  two 
parts — namely,  paving,  which  is  a  floor  surface  laid  and 
resting  on  solid  ground;  and  floors,  by  which  are  meant 
floors  over  voids.  The  following  items  briefly  embody 
the  processes  used  for  most  concrete  pavings  now  in 
use.  Paving  in  situ  is  either  laid  in  ^'one  coat''  or 
^Hwo  coats,"  the  latter  being  in  more  general  use  than 


HOW  TO  USE  THEM 


311 


the  former,  yet  each  method  has  its  individual  merits. 
One-coat  work  is  not  so  liable  to  rise  or  laminate  as  two- 
coat  work.  It  takes  slightly  less  labor,  the  whole  thick- 
ness being  laid  in  one  operation.  The  aggregate  is 
either  granite  or  slag,  or  both  in  equal  proportions, 
gauged  with  Portland  cement  in  the  proportion  of  2  of 
the  latter  to  5  of  the  former.  Two-coat  is  laid  with 
two  different  aggregates  and  gauges.  The  first  coat  has 
a  cheap  aggregate,  such  as  ballast,  clinkers,  bricks,  or 
wliinstone,  broken  so  that  they  will  pass  through  a  1 
inch  mesh  riddle,  and  gauged  in  the  ratio  of  1  of  Port- 
land cement  to  5  of  the  aggregate.  It  is  laid  till  within 
1  inch  of  the  finished  surface.  The  second  coat  is  laid 
as  soon  as  the  first  is  set,  and  is  composed  of  1  part  of 
Portland  to  2  of  the  aggregate,  the  latter  being  either 
crushed  granite,  slag,  limestone,  or  whinstone  that  will 
pass  through  a  3-16  sieve.  In  some  districts  fine  shingle 
is  used  for  the  topping  aggregate. 

Quick-setting  solutions  are  used  to  reduce  the  time  re- 
quired to  allow  the  paving  to  harden  before  it  is  avail- 
able for  traffic.  Many  pavements  are  ruined  by  being 
used  before  having  become  sufficiently  hard  and  set. 
Many  of  the  so-called  quick-setting  materials  have  the 
desired  effect  of  setting  the  concrete  quickly,  but  the 
work  in  many  cases  is  none  the  better  for  these  solutions. 
On  no  account  should  these  quick-setting  materials  be 
used,  unless  thoroughy  tested  and  the  concrete  proved 
durable  by  use  and  time.  In  order  to  protect  the  sur- 
face and  allow  the  paving  to  be  used  immediately,  P.  M. 
Bruner,  an  American  engineer  and  concrete  specialist, 
covers  the  surface  of  the  pavement  directly  it  is  finished 
with  a  thin  coat  of  plaster  or  Parian  cement,  which  ad- 
mits of  walking  upon  in  a  few  hours,  and  resists  pedes- 


312  CEMENTS  AND  CONCRETES 


trian  traffic  until  the  surface  proper  is  sufficiently  hard, 
after  which  it  is  shelled  olf  with  a  trowel. 

Eureka  Paving. — This  is  the  name  for  an  improved 
cont^rete,  which  has  been  extensively  used  with  good  re- 
sults for  many  purposes,  such  as  pavements,  floors  and 
stairs.  Eureka,  if  not  exactly  one-coat  work,  is  nearer 
that  than  two-coat  work,  and  may  be  said  to  be  the 
happy  medium,  or  a  combination  of  both.  Eureka  is 
laid  in  two  layers.  The  first  is  termed  the  ''rough 
coat,''  and  the  second  the  ''fine  coaf  or  "topping." 
The  topping  is  laid  nearly  as  soon  as  the  rough  coat  is 
laid,  just  as  in  rendering  or  dubbing-out  plaster  work. 
The  materials  and  gauges  are  nearly  alike  for  both 
layers.  The  gauged  rough  stuff  is  laid  on  the  founda- 
tion, previously  wetted  to  prevent  suction,  and  spread 
and  beaten  with  an  iron  hand-float.  The  laying,  spread- 
ing and  beating  is  continued  until  the  rough  surface 
is  within  I/2  inch  of  the  finished  line.  The  surface  of 
the  rough  coat  is  made  fair,  and  a  uniform  thickness 
for  the  topping  is  obtained  by  passing  a  "gauge-rule" 
across  the  surface.  A  uniform  thickness  of  topping 
gives  an  equal  expansion,  therefore  the  surface  is  not 
liable  to  crack.  The  suction  is  also  more  regular,  which 
permits  of  the  trowelling  to  be  done  with  greater  free- 
dom, and  without  causing  hard  and  soft  places  on  the 
surface. 

As  many  alternate  bays  are  laid  as  will  allow  of  all 
being  topped  and  finished  the  same  day.  When  the 
number  of  bays  to  be  laid  in  on  one  day  has  been  de- 
cided, and  the  last  one  roughened  in,  the  first  bay  will 
be  firm  to  receive  the  topping.  The  topping  is  laid  and 
spread  with  a  wooden  hand-float,  ruled  and  trowelled 
and  brushed  as  afterwards  described  in  the  general  pro 
cess.    This  method  of  laying  a  part  of  the  thickness  ot 


HOW  TO  USE  THEM 


313 


the  paving,  gauging  stiff  and  beating  the  mass,  forces 
it  into  the  interstices  of  the  broken  dry  foundation,  and 
not  only  consolidates  the  foundation  and  the  rough  coat, 
but  also  forms  a  solid  bed  to  receive  the  topping.  The 
topping  goes  in  sooner  and  more  regularly  on  a  stiff- 
gauged  and  well-beaten  coat  than  on  a  soft-gauged  one, 
or  than  if  the  whole  thickness  of  the  paVing  were  laid 
in  one  coat. 

Eureka  Aggregate, — The  method  of  preparing  the  ag- 
gregate for  Eureka  is  of  the  utmost  importance.  The 
labor  expended  on  its  preparation  is  more  than  repaid, 
not  only  in  the  ease  and  rapidity  when  finishing,  but  also 
in  the  satisfaction  of  doing  a  strong  and  workmanlike 
job.  Slag  and  granite  is  far  more  preferable  to  gravel 
or  stone  as  an  aggregate.  Slag  and  granite  in  equal 
proportions  have  been  used  with  good  results.  The  size 
ordered  from  the  furnace  or  quarry  should  be  %  inch 
screenings.  It  must  be  washed  through  a  %  inch  sieve 
in  a  tub  or  iron  tank.  The  coarse  part  rejected  by  the 
sieve  to  be  laid  aside  for  the  rough  coat.  The  fine  ag- 
gregate is  then  washed  again  through  a  fine  sieve  to  ex- 
tract any  mud  or  impalpable  powder,  as  the  presence  of 
such  impurities  weakens  the  consolidating  power  of  the 
cement,  and  decreases  the  ultimate  strength  of  the  con- 
crete. This  fine  aggregate  for  the  topping  should  be 
angular  and  of  various  graduating  sizes,  from  that  of 
fine  sharp  sand  to  the  largest  size  that  has  passed  through 
the  %  inch  sieve.  It  has  been  proved  by  experience  and 
the  test  of  time  that  an  artificial  stone  made  with  a  fine 
aggregate  has  not  only  more  resemblance  to  the  grain  or 
texture  of  natural  stone,  but  is  also  denser,  and  wears 
better  and  with  more  uniformity,  than  one  made  with  a 
large,  round,  or  equal-sized  aggregate.  The  use  of  small 
and  angular  aggregate  of  the  graduating  sizes  ensures 


314  CEMENTS  AND  CONCRETES 


their  fitting  closer  and  interlocking  together,  thus  form- 
ing a  stronger  bond,  giving  a  regular  key  and  freedom 
for  each  separate  piece  to  be  coated  with  cement,  the 
whole  forming  a  solid  and  homogeneous  body  with  a 
hard  surface.  Concrete  with  large  or  round  aggregate, 
and  the  various  pieces  disproportionate  in  size  to  each 
other,  will  fit  loosely  and  unevenly,  and  only  touch  at 
their  most  prominent  points,  thus  leaving  voids,  and  con- 
sequently unsound  work.  The  voids  may  perchance  be 
wholly  or  partly  filled  with  matrix,  still  this  is  an  un- 
necessary waste  of  cement.  Consequently,  concrete  pav- 
ing having  large  or  round  aggregate  wears  unevenly,  and 
leaves  the  large  or  round  pieces  uncoated  and  loose,  or 
so  exposed  above  the  surface  that  they  soon  get  dis- 
lodged, leaving  a  series  of  small  holes,  which  sooner  or 
later  wear  larger  and  larger.  Another  point  of  import- 
ance is  that  concrete  with  a  fine  hard  aggregate  is  more 
plastic,  works  freer,  and  has  a  greater  compressive 
strength  than  concrete  with  a  large  or  soft  aggregate. 
Eureka  concrete,  having  a  fine^  clean,  and  regulated  ag- 
gregate, should  be  used  for  the  topping  of  paving,  steps, 
landings,  or  for  any  class  of  work  exposed  to  friction  or 
wear.  It  is  well  to  remember  that  a  good  matrix  will 
not  make  a  bad  aggregate  strong,  although  a  bad  ag- 
gregate will  make  a  good  matrix  weak,  or  rather  the  re- 
sultant concrete  weak. 

Eureka  Quantities, — The  quantities  for  the  rough 
coat  are  1  part  of  Portland  cement  and  4  parts  of  the 
coarse  portion  of  Eureka  aggregate.  These  materials 
must  be  gauged  stiff,  only  as  much  water  being  used  as 
will  allow  the  mass  to  be  thoroughly  mixed  and  plastic. 
The  quantities  for  the  topping  are  2  parts  of  Portland 
cement  to  5  of  the  fine  aggregate,  and  gauged  about  the 
consistency  of  well-tempered  ''coarse  stuff,"  as  used  for 


HOW  TO  USE  THEM 


315 


floating.  Experiments  prove  that  neat  cement  is  infe- 
rior in  wear-resisting  qualities  (sueh  as  frictional  wear 
and  pedestrian  traffic)  to  mixture  of  cement  with  sand 
or  other  aggregate,  being  in  fact  equal  to  a  mixture  of 
about  1  part  of  cement  to  3  parts  of  aggregate.  The 
best  wearing  qualities  are  obtained  by  a  mixture  of  2 
parts  of  cement  to  3  of  aggregate. 

Levels  and  Falls. — Accurate  levelling  and  adjustment 
of  the  requisite  falls  are  important  features  for  pave- 
ments and  flooring.  Levelling  is  the  art  by  which  the  rel- 
ative heights  of  any  number  of  points  are  determined. 
Falls  are  used  to  allow  rain  and  water  used  for  cleansing 
purposes  to  run  off  into  channels  and  drains.  The  levels 
and  falls  in  good  buildings  are  generally  marked,  on  the 
drawings,  but  it  is  imperative  that  the  worker  should  be 
conversant  with  the  necessary  amount  of  falls  for  paving 
purposes,  as  many  unforeseen  difficulties  often  arise  in 
this  class  of  work,  especially  in  large  surfaces.  The  most 
accurate  and  speedy  way  of  setting  out  levels  and  falls 
is  of  special  service  to  concrete  paviors.  The  importance 
of  these  features  will  be  readily  appreciated,  especially 
where  these  paving  preliminaries  are  left  to  the  care  of 
the  concrete  layers.  The  amount  of  cross  fall  for  street 
pavements  varies  according  to  the  class  and  position  of 
the  work.  The  fall  is  also  regulated  by  the  gradient.  For 
a  level  stretch  of  paving  it  is  generally  1  to  60,  therefore 
for  a  pavement  6  feet  wide  it  would  be  1  inch.  The  fall 
for  rising  ground  is  usually  %  inch  for  every  2  feet  in 
the  width  of  the  pavement.  The  falls  for  stables  and 
yards  are  given  under  their  respective  headings.  The 
points  for  levelling — also  for  falls — are  formed  by  driv- 
ing wooden  pegs  into  the  ground  at  the  most  suitable 
points.  The  heads  of  the  pegs  represent  the  finished  face 
of  the  pavement.    They  are  made  level  with  each  other 


316  CEMENTS  AND  CONCRETES 


by  the  aid  of  a  parallel  rule  and  a  spirit-level.  Inter- 
mediate pegs  may  also  be  levelled  by  means  of  boning 
rods. 

Pavement  Foundations — Good  foundations  for  con- 
crete paving  are  of  primary  importance,  and  unless  the 
bottom  is  firm,  and  the  foundation  is  sound,  the  best 
made  and  laid  concrete  will  subside,  crack,  and  be  per- 
manently spoilt.  Pavements  generally  cover  a  large 
area,  and  the  superstructure,  however  strong,  must  have 
a  firm  foundation.  Foundations  consist  of  two  parts — 
the  first  is  the  bottom  ground  or  natural  foundation ;  the 
second  is  the  made-up  or  artificial  foundation;  but  for 
simplicity  the  first  is  termed  the  ^'bottom,''  and  the  lat- 
ter the  ''foundation.''  The  latter  may  be  "dry"  or 
■'gauged."  If  the  bottom  is  soft,  it  must  be  well  ram- 
med before  laying  the  dry  materials  for  the  foundation, 
or  a  layer  of  common  coarse  concrete  for  gauged  work. 
When  excavating  the  ground  to  receive  the  foundation, 
the  depth  from  the  intended  finished  surface  of  the 
pavement  should  be  about  5  inches  for  paving  2  inches 
thick,  6  inches  deep  for  paving  2%  inches  thick,  and  7 
inches  deep  for  paving  3  inches  thick.  The  above  depths 
are  for  dry  foundations,  and  where  the  traffic  is  light, 
such  as  side-walks,  playgrounds,  and  passages.  If  the 
bottom  is  soft,  or  the  paving  intended  for  heavy  traffic, 
the  depths  may  be  increased,  and  the  bottom  well  ram- 
med before  the  materials  are  laid.  The  materials  for  the 
dry  foundations  are  broken  bricks,  stone  rubble,  or  other 
hard  core.  They  should  be  spread  on  the  bottom,  and 
broken  in  situ.  The  breaking  in  situ  tends  to  consoli- 
date the  bottom  and  the  foundation.  When  broken,  no 
piece  should  be  left  that  will  not  pass  through  a  2l^  inch 
ring.    If  the  paving  is  intended  for  heavy  traffic  (carts 


HOW  TO  USE  THEM 


317 


or  the  rolling  of  heavy  casks)  it  is  best  to  have  a  rough 
concrete  foundation.  The  rough  concrete  should  be 
from  4  to  7  inches  deep,  according  to  the  firmness  of  the 
bottom  and  class  of  traffic.  This  concrete  is  composed 
of  ballast  or  equal  parts  ballast  and  broken  bricks,  coke- 
breeze,  or  hard  clinkers,  gauged  in  the  proportion  of  1 
of  Portland  cement  to  5  or  6  of  aggregate.  It  should  be 
laid  to  the  desired  fall.  If  lime  instead  of  Portland  ce- 
ment is  used  for  the  rough  concrete,  great  care  should 
be  taken  to  thoroughly  damp  the  surface,  and  allow  a 
sufficient  time  for  the  lime  to  expand  and  any  lumps  of 
unslaked  lime  to  slake,  before  the  fine  concrete  is  laid.  No 
paving  should  be  laid  until  the  rough  concrete  is  thor- 
oughly set.  Allowance  must  also  be  made  for  any  set- 
tlement of  the  bottom^  and  for  any  subsidence,  contrac- 
tion, or  expansion  of  the  concrete  foundation.  The 
rough  is  not  so  liable  to  contraction  or  expansion  as  fine 
concrete,  but  it  is  more  liable  to  subsidence.  Expansion 
is  due  to  the  cement  not  to  the  aggregate ;  and  as  there  is 
less  cement  in  rough  concrete  than  in  fine,  it  has  less 
power  of  expansion,  and  owing  to  the  greater  amount 
and  weight  of  aggregate,  there  is  the  lesser  power  of  con- 
traction. The  size  of  aggregate  for  rough  concrete  is 
also  larger  than  for  fine ;  consequently  each  piece  offers 
a  greater  resistance  to  the  cement.  Subsidence  is  due  to 
the  settlement  by  gravitation  of  the  aggregate  to  the  bot- 
tom, which  takes  place  after  the  excess  water,  or  even 
the  liquid  cement,  has  percolated  through  voids  or  spaces 
of  badly  made  or  laid  concrete.  Unequal  subsidence  is 
caused  by  bad  and  unequal  gauging;  one  gauge  being 
firm,  keeps  in  position ;  while  if  soft  and  sloppy,  the  ex- 
cess water  either  settles  in  the  deepest  places,  or  escapes 


S18  CEMENTS  AND  CONCRETES 


into  the  ground,  thus  allowing  the  body  of  the  concrete 
at  those  parts  to  subside. 

Screeds  and  Sections, — Screeds  are  used  as  guides  and 
bearings  for  leveling  and  ruling  off.  They  are  general- 
ly formed  with  wood  rules,  planed  on  all  sides,  and  in 
suitable  sizes,  and  are  termed  ^'screed  rules."  Screeds 
are  sometimes  formed  with  the  same  kind  of  material  as 
used  for  the  pavement,  and  are  termed  ^ '  gauged  screeds. '  ^ 
Screed  rules  give  the  best  results ;  they  are  speedily  laid ; 
can  be  used  at  once,  and  form  a  clean  and  square  joint 
when  laying  work  in  sections.  Screed  rules  are  tempo- 
rarily fixed  on  the  foundation  by  laying  them  on  narrow 
strips  of  gauged  concrete,  and  then  made  straight,  and  to 
the  proper  falls,  by  laying  the  edge  of  a  straight-edge  on 
them,  and  tapping  with  a  hammer  till  firm  and  true. 
When  the  bay  is  finished  and  set,  the  screeds  are  re- 
moved by  gently  tapping  with  a  hammer,  leaving  a  clean, 
straight,  and  square  joint.  Where  there  is  only  a  small 
quantity  of  screeds  required,  or  where  time  will  not  per- 
mit of  waiting  for  the  concrete  bedding  strips  to  set,  the 
screed  rules  can  be  fixed  on  gauged  plaster,  which  al- 
lows the  screeds  to  be  used  at  once.  The  plaster  should 
be  cleaned  off  at  the  side  intended  to  be  laid;  to  ensure  a 
sound  bed  for  the  concrete,  and  a  square  joint.  Gauged 
screeds  may  be  also  formed  with  gauged  coarse  plaster. 
They  are  best  done  as  described  for  ''pressed  screeds." 
In  laying  large  surfaces  it  is  best  to  arrange  the  screeds, 
so  that  the  work  can  be  laid  in  alternate  sections  or  bays, 
w^hich  will  afford  greater  facility  to  get  at  the  work,  and 
also  to  allow  the  isolated  bays  to  expand.  For  instance, 
if  laying  a  stretch  of  paving  50  feet  long  and  6  feet  wide, 
this  would  be  laid  out  in  5-feet  bays,  the  screed  rules, 
each  6  feet  long,  being  laid  so  as  to  form  the  odd  num- 


HOW  TO  USE  THEM 


319 


bered  bays  to  be  laid  and  finished  first.  This  allows  the 
workmen  more  freedom  by  standing  on  the  empty  bays 
when  finishing  the  laid  bay.  The  screeds  are  then  re- 
moved, and  the  intermediate  bays  laid,  the  sides  of  the 
finished  bays  serving  as  screed  or  bearing  when  ruling 
in.  Boards  or  bags  are  laid  on  the  finished  bays  to  pro- 
tect the  surface,  and  give  a  footing  for  a  workman  to 
finish  off  the  intermediate  spaces.  It  must  not  be  for- 
gotten to  fix  the  screed  rules  toward  the  curbs,  also  to 
keep  the  ends  of  the  screed  about  %  inch  about  the  curb, 
to  allow  for  any  subsidence,  and  for  the  water  to  run 
off.    This  also  provides  for  the  greater  amount  of  wear 


Sections  of  Concrete  Kerb,  Channel,  and 
Paving. 

NO.  1. 


that  takes  place  near  to  than  actually  on  the  curb.  The 
foundations  should  be  thoroughly  saturated  with  water 
before  the  screeds  are  fixed.  If  this  is  not  done,  the 
brick  or  other  dry  material  used  will  absorb  the  moisture 
or  life  from  the  concrete,  and  render  it  dry  or  dead.  The 
drenching  with  water  also  frees  the  broken  materials 
from  the  dust  caused  by  breaking  the  large  pieces  in 
situ.  In  laying  paving  or  a  gauged  foundation,  the  sur- 
face should  be  well  swept  with  a  hard  broom  and  after- 


320  CEMENTS  AND  CONCRETES 


wards  damped,  so  as  to  ensure  the  perfect  cohesion  and 
solidity  of  the  foundation  and  the  paving.  The  curbs 
and  channels  are  sometimes  made  in  situ,  but  more  often 
they  are  cast  and  laid  in  the  same  manner  as  ordinary 
stone.  Cast  work  is  harder  than  laid  work;  it  also  al- 
lows the  paving  to  be  laid  with  greater  freedom.  Illus- 
tration No.  1  shows  sections  of  the  street  curbing  and 
channel  which  may  be  used  in  connection  with  slab  pav- 
ing, or  pavements  laid  in  situ. 

Laying  Concrete  Pavements. — The  foundations  having 
been  damped,  and  the  rough  stuff  gauged,  it  is  carried 
in  pails  and  emptied  at  the  top  end  of  the  bay.  The  plas- 
terer spreads  it  with  a  layer  float,  and  rams  it  well  into 
the  foundation.  When  he  has  laid  a  stretch  the  whole 
width  of  the  bay,  and  as  far  as  he  can  conveniently  reach, 
he  moves  back  and  lays  the  remaining  portions  of  the 
bay  in  the  same  way  until  complete.  The  rough  stuff 
surface  is  then  made  fair,  but  not  smooth,  with  the  gauge 
rule.  The  remainder  of  the  bays  are  dealt  with  in  rota- 
tion. The  fine  aggregate  is  then  gauged,  and  laid  and 
spread  until  flush  with  the  screeds.  The  stuff  should  be 
rather  above  than  below  the  screeds,  to  allow  for  subsi- 
dence by  subsequent  ramming,  ruling  and  patting.  All 
concrete  bodies  over  2  inches  thick  should  be  deposited 
in  layers.  Each  layer  should  be  well  rammed  with  an 
iron,  or  hardwood  temp,  bound  with  iron.  Concrete 
gains  strength  by  compression,  and  consequently  its 
density,  imperviousness,  and  durability  are  increased. 
Even  for  2  inch  pavement  better  results  are  obtained  if 
the  stuff  is  deposited  in  two  layers,  each  layer  well 
beaten  with  an  iron  hand-float.  If  only  II/2  inches  thick, 
it  should  be  consolidated  by  being  beaten  with  an  iron 
float.    The  surface  is  next  ruled  with  a  floating  rule. 


HOW  TO  USE  THEM 


321 


The  rule  is  worked  square  or  edge,  and  the  concrete  cut 
and  beaten  in  successive  short  and  quick  strokes.  If  the 
stuff  is  soft  and  laid  too  full,  the  rule  is  worked  loosely 
on  edge  with  a  zigzag  motion,  so  as  to  draw  the  excess 
stuff  and  water  off  the  surface,  and  leave  the  body  full 
and  regular.  If  there  are  any  hollow  places,  they  are 
filled  up  with  stuff,  and  the  rule  again  applied.  '  In  all 
cases  the  surface  should  be  finally  straightened  by  beat- 
ing with  the  rule.  This  process  leaves  the  surface  more 
uniform,  straight,  and  solid  than  by  dragging  or  working 
the  rule. 

Trowelling  Concrete. — After  being  ruled,  and  when 
slightly  firm,  the  surface  is  beaten  with  a  wood  hand- 
float,  which  lays  any  irregular  parts  or  projecting  pieces 
of  aggregate.  The  beating  or  patting  is  continued  until 
the  ''fat"  appears  on  the  surface.  It  is  then  trowelled, 
or  rather  ironed,  the  trowel  being  worked  on  the  fiat  of 
the  blade  with  a  circular  motion.  The  plasterer,  when 
trowelling  off,  should  have  a  hand-float  in  the  other 
hand  to  lean  on  when  reaching  to  a  far  off  part.  The 
float  is  also  useful  to  pat  any  dry  parts.  The  surface 
must  be  finished  with  a  semi-dry  stock-brush  to  obtain  a 
uniform  grain.  A  vast  amount  of  care  is  required  in 
trowelling  off.  Perfection  can  only  be  attained  by  prac- 
tice, and  a  close  observation  of  the  materials,  conditions, 
and  the  state  of  the  atmosphere  during  the  progress  of 
the  work.  The  best  effects  can  only  be  attained  by 
acquiring  a  knack  of  working  the  trowel  on  the  fiat,  and 
by  knowing  when  to  begin  and  when  to  leave  off.  It  is  a 
waste  of  time,  and  the  cause  of  an  unequal  surface,  if 
the  trowelling  is  begun  before  the  stuff  is  firm;  but  time 
and  labor  will  also  be  lost  if  the  trowelling  is  left  until 
the  stuff  is  too  stiff,  or  has  nearly  set,  for  then  the  sur- 


822  CEMENTS  AND  CONCRETES 

face  will  be  rough  and  patchy.  In  either  instance  the 
surface  is  more  or  less  spoilt,  and  the  ultimate  appear- 
ance and  hardness  seriously  affected. 

Grouting. — The  use  of  neat  cement  for  trowelling  off 
should  not  be  resorted  to  (this  is  termed  grouting''), 
and  is  used  when  the  surface  is  left  till  set,  or  when  it 
has  not  been  properly  patted  and  trowelled.  The  ex- 
pansion of  a  strong  and  weak  gauge  being  unequal,  the 
result  is  that  the  surface  peels,  or  should  it  adhere,  it  is 
patchy  and  discolored.  Where  grouting  is  unavoidable, 
the  cement  should  be  gauged  with  an  equal  part  of  fine 
aggregate,  the  aggregate  being  the  same  as  used  for  the 
topping. 

Dusting. — Another  bad  process  is  that  of  sprinkling 
dry  neat  cement  over  a  soft  surface  (this  is  termed 
''dusting"),  and  is  used  to  absorb  the  moisture  caused 
by  sloppy  gauging.  It  has  draw^backs  similar  to  grout- 
ing. If  unavoidable,  the  cement  should  be  mixed  with 
line  dry  aggregate  in  the  same  proportion  as  the  topping. 
If  the  stuff  were  trowelled  at  the  correct  time,  there 
would  be  no  necessity  for  grouting;  and  if  properly 
gauged,  no  need  for  dusting.  No  concrete  surface  can  be 
made  so  solid  and  hard  as  when  it  is  finished  in  one  body 
and  at  one  time. 

Temperature. — It  is  well  known  that  extreme  heat  and 
cold  effect  the  expansion  and  contraction  of  iron.  These 
extremes  have  a  similar  effect  on  concrete,  especially  dur- 
ing the  process  of  setting  and  hardening.  Equality  of 
temperature  during  setting  is  desirable.  Cold  and 
humid  atmosphere  retard  setting;  hot  humidity  acceler- 
ates it.  Concrete  laid  in  cold  weather  stands  better 
than  that  laid  during  hot.  Concrete  laid  in  mild  damp 
weather  is  better  than  in  either  extreme.    During  high 


HOW  TO  USE  THEM 


323 


temperatures,  the  surface,  when  sufficiently  hard,  should 
be  covered  with  damp  deal  saw-dust,  old  sacks,  mats,  or 
sail-cloth,  and  saturated  at  intervals  with  water.  If  the 
sun's  rays  are  hot,  the  surface  of  the  work  while  in 
progress  should  be  protected  by  extending  tarpaulin  or 
sail-cloths  above  the  parts  being  laid.  Concrete  surfaces 
are  further  hardened  by  flooding  with  water,  or  where 
this  is  not  practical,  covering  with  wet  saw-dust  or  sand 
as  soon  as  set.  Care  must  be  taken  that  the  saw-dust  is 
clean  and  of  a  light  color,  as  otherwise  it  will  stain  the 
work. 

Non-Slippery  Pavements. — Concrete  pavements  for 
special  purposes  are  rendered  non-slippery  by  mixing  Vg 
inch  lead  cubes  with  the  topping  stuff.  Lead  cubes  about 
Y2  iiich  square  laid  by  hand  from  1  inch  to  4  inches 
apart  in  the  moist  concrete  surface,  have  been  used  for 
rendering  concrete  surfaces  non-slippery.  Iron  and 
brass  filings  are  also  used  for  the  same  purpose,  and  also 
for  increasing  the  wear-resisting  of  concrete  surface. 
Roughened,  indented,  grooved,  and  matted  surfaces  are 
also  used  to  obtain  a  better  foot-hold  on  concrete  sur- 
faces. 

Grooved  and  Roughened  Surfaces. — Stables,  yards, 
&c.,  are  grooved  and  channeled  on  the  surfaces  to  pre- 
vent animals  from  slipping,  and  also  to  carry  off  urine 
or  other  liquids  to  the  traps  or  guUeys.  Indented  sur- 
faces are  useful  on  steep  gradient  to  give  a  better  foot- 
hold. Grooves  are  made  with  a  special  wood  or  iron 
tool,  which  is  beaten  into  the  surface  as  soon  as  the  con- 
crete is  floated.  The  grooves  for  stables  are  generally 
made  about  5  inches  from  centre  to  centre,  and  the  depth 
about  %  inch.  A  line  is  first  made  at  the  one  end  of  the 
work,  and  the  groover  is  then  laid  on  this  line,  and  beat- 


324 


CEMENTS  AND  CONCRETES 


en  down  with  a  hammer  to  the  desired  depth.  Before  it 
is  taken  off,  a  parallel  rule  is  laid  on  the  surface  and 
against  the  groover,  which  is  then  taken  up  and  laid 
close  to  the  other  side  of  the  parallel  rule,  and  beaten 
in  as  before,  and  so  on  until  the  whole  surface  is  done. 
The  width  of  the  parallel  rule  is  equal  to  the  desired 
width  between  the  grooves,  less  the  width  of  the  groover. 
Grooves,  however  long,  can  be  made  by  moving  the  tool 
along,  and  against  a  long  parallel  rule.  After  stretch  of 
grooves  have  been  sunk,  the  surface  is  trowelled,  and  the 
indentations  made  true.  It  may  be  necessary  to  apply 
the  groover  again,  and  beat  or  work  it  forward  and  back- 
ward and  further  regulate  their  depth  and  straightness. 
They  are  then  made  smooth  with  a  gauging  trowel  and 
finished  with  a  damp  brush,  the  sides  of  the  grooves  being 
left  smooth  to  give  a  free  passage  for  liquids. 

Grooves  on  a  surface  having  a  fall  should  radiate  to- 
ward the  deepest  point.  A  level  surface  may  be  made 
to  carry  off  the  water  by  the  indentation  being  formed 
wider  and  deeper  towards  the  outlet.  Street  and  other 
pavements  are  sometimes  indented  with  metal  rollers  to 
give  a  better  foot-hold.  Platforms  and  other  surfaces  are 
sometimes  made  rough  or  indented  by  beating  the  moist 
concrete,  with  a  ' '  stamping-float. ' '  The  sole  has  a  series 
of  squares  projecting  about  %  inch,  each  square  about 
1  inch,  and  a  half  inch  apart.  Concrete  surfaces  are  al- 
so roughened  or  matted  by  dabbing  the  surface  as  soon 
as  trowelled  with  a  coarse  stiff  whale-bone  brush.  Illus- 
tration No.  2  shows  three  designs  of  grooved  surfaces  for 
carriage  drives,  conservatories,  &c.  A  plain  border,  or 
one  with  a  single  width  of  the  main  design,  is  generally 
formed  on  the  sides  and  ends  of  the  floor.    A  rough  mat- 


HOW  TO  USE  THEM 


325 


ted  surface  may  also  be  obtained  by  pressing  or  beating 
a  wet  coarse  sack  or  matting  over  the  moist  concrete. 

Stamped  Concrete. — Various  materials  and  methods 
are  used  for  stamping  or  indenting  concrete  surfaces  to 
obtain  a  better  foot-hold,  or  to  form  any  desired  pattern. 
Iron  stamps  are  generally  used,  but  owing  to  their 
weight  and  rigid  nature,  are  unsuitable  for  large  sec- 
Fig.  I.  Fig.  2.  Fig.  3. 


m\ 

=4  1 

^^^^^^^ 

=^■111 

Three  Examples  of  Grooved  Surfaces. 
NO.  2. 


tions.  Plaster  stamps  are  sometimes  used  for  temporary 
purposes,  or  for  small  sections  and  quantities.  Stamps 
for  large  concrete  surfaces  should  be  composed  of  a  ma- 
terial that  is  easily  made  to  the  desired  form  durable 
and  slightly  flexible. 

Expansion  Joints, — Compressive  or  flexible  joints  are 
used  to  allow  for  any  expansion  or  contraction  that  may 
take  place  in  a  large  area  of  concrete  exposed  to  atmos- 
pheric changes.    There  are  various  methods  in  use  for 


326  CEMENTS  AND  CONCRETES 

the  purpose.  The  first  is  to  set  out  the  area  in  small 
sections,  and  to  lay  them  in  alternate  or  isolated  bays, 
thus  giving  time  for  their  expansion  before  the  inter- 
mediate bays  are  laid.  This  method,  by  dividing  the 
area  into  small  sections,  is  the  best  for  preventing  cracks, 
because  small  sections  are  stronger  than  large  ones ;  and 
in  the  event  of  any  subsidence  in  the  foundation,  the 
surface  fissures  are  limited  to  the  immediate  joints  of 
the  section.  Contraction  and  expansion  is  also  less  in 
small  bodies  than  in  larger  ones. 

Another  method  of  forming  joints  is  by  cutting  with  a 
wide  chisel  or  a  cutting  tool  before  the  rough  concrete  is 
set,  a  corresponding  joint  being  cut  in  the  fine  concrete 
topping.  False  joints  are  made  by  indenting  the  top- 
ping after  it  is  trowelled.  A  metal  roller  is  used  for 
finishing  true  joints  and  forming  false  joints.  Frame 
strong  enough  to  resist  the  expansion  of  the  concrete 
would  not  only  increase  the  density  and  strength  of 
concrete  paving  and  blocks,  but  also  effectually  prevent 
its  cracking. 

Another  method  for  forming  sections  in  large  sur- 
faces of  pavement  of  floors  to  prevent  cracks  is  effected 
thus: — first  set  out  the  size  of  proposed  sections  on  the 
rough  or  first  coat,  then  with  a  straight-edge,  a  wide 
chisel,  or  a  cutting  tool  and  a  hammer,  cut  through  the 
rough  coat,  so  as  to  divide  it  into  sections  as  set  out. 
This  done,  insert  wood  strips  into  the  cutting,  keeping 
their  top  edges  about  i/8  iiich  below  the  screeds  or  rules 
which  represent  the  finished  surface.  The  strips  are 
made  from  %  to  1%  inches  wide,  3-16  inch  thick,  and  in 
suitable  lengths.  The  width  is  regulated  according  to 
the  thickness  of  the  paving.  For  instance^  for  two  inch 
paving  the  widths  should  be  1%  inches.    This  allows 


HOW  TO  USE  THEM 


327 


about  %  inches  in  the  rough  coat  (with  l^  inch  play 
from  the  bottom),  and  about  %  inch  in  the  topping,  and 
Vg  inch  for  the  upper  thickness  of  the  topping  to  cover 
the  top  edges  of  the  strips.  After  the  strips  are  inserted 
the  rough  coat  is  beaten  up  or  made  good  to  the  sides  of 
the  strips,  and  then  the  topping  is  laid  and  trowelled  in 
the  usual  way.   The  surface  joints  are  then  made  direct- 


-Half  Plan  of  Coach  Yard,  with 
Section  through  Centre. 

NO.  3. 

ly  over  the  strips,  with  the  aid  of  a  straight  edge,  so  as 
to  form  a  clean  and  sharp  joint.  As  already  mentioned, 
these  strips  allow  for  any  subsequent  contraction  or  ex- 
pansion, thus  avoiding  zigzag  cracks ;  and  in  the  event  of 
repairs  to  underneath  pipes,  each  section  can  be  cut  out 
and  relaid  separately  without  injury  to  the  adjoining 
sections.  This  process  of  inserting  strips  in  the  rough 
coat,  cutting  nearly  through  the  topping,  gives  the  same 
results  as  if  the  strips  were  laid  flush  with  the  surface 
of  the  topping,  with  the  advantages  that  the  surface  can 
be  more  readily  trowelled,  and  is  more  pleasing  to  the 


328 


CEMENTS  AND  CONCRETES 


eye,  because  the  strips  are  not  seen.  A  cutting  tool  is  a 
blade  of  steel  about  5  or  6  inches  long  and  4  inches  wide, 
with  a  wood  handle  at  one  end.  The  section  of  the  blade 
is  well  tapered,  so  as  to  obtain  a  sharp  cutting  edge,  and 
form  a  wide  top  edge  to  offer  a  broad  surface  for  the 
hammer  while  being  beaten. 

Washing  Yards4 — Eureka  concrete  being  of  a  hard 
nature,  and  having  a  close  and  smooth  surface,  is  well 
adapted  as  a  flooring  for  all  washing  or  cleaning  pur- 
poses. The  surface  being  smooth,  it  can  in  turn  be  read- 
ily cleaned.  Illustration  No.  3  shows  the  half  plan  of 
washing  yard  for  washing  carriages,  &c. 

Stahle  Pavements. — The  paving  for  stables,  and  other 
places  for  keeping  animals,  should  be  jointless,  non-ab- 
sorbent, hard,  and  durable.  Such  paving  must  not  be 
slippery,  yet  smooth  enough  to  be  easily  washed,  the 
whole  laid  to  falls,  and  grooved  to  give  an  easy  and 
ready  passage  for  liquid  manure  and  water  when  being 
washed.  No  material  can  so  fully  meet  these  require- 
ments as  a  well-made  and  well-laid  concrete.  Granite 
sets  are  hard,  but  slippery.  Bricks  are  too  absorbent; 
the  urine  percolates  between  the  joints  and  generates 
ammonia  and  other  effluvia  which  are  detrimental  to  the 
health  of  the  animals.    (See  Nos.  4  and  5.) 

Stables  are  generally  laid  with  a  fall  toward  the  main 
channel.  The  amount  of  fall  varies  according  to  ideas 
of  the  horse  owners.  The  fall  adopted  by  the  War  office  is 
1  in  80  from  the  top  of  the  manger  to  the  main  channel, 
and  1  to  36  from  each  side  of  the  stall  to  the  centre  groove. 
The  width  of  the  main  channels  is  usually  set  out  with 
screed  rules,  which  also  act  as  screeds  to  work  from.. 
Channels  are  generally  formed  after  the  other  surface  is 
finished.    Sometimes  templates  are  fixed  on  the  bed  of 


HOW  TO  USE  THEM 


329 


the  channels,  and  the  space  filled  in  and  ruled  off  with  a 
straight-edge  while  the  whole  surface  is  being  formed. 
The  thickness  of  stable   paving  varies  from  2  to 
inches,  according  to  the  class  of  horse.    The  thickness  of 
the  stalls  is  often  decreased  toward  the  manger. 

The  most  useful  length  is  2  feet  6  inches.  They  can 
be  cut  with  a  chisel  as  easy  as  cutting  stone.  Special 
slabs  can  be  made  for  circular  work,  also  with  rebated 
sinking  for  metal  plates,  to  cover  coal-holes,  drains,  gas 
and  w^ater  taps,  &c.  Concrete  paving  slabs  are  laid  in 
precisely  the  same  way  as  natural  stone. 


....  ^^^^y^^-^-'^^^  fP.  »  -  /Sechon  <f  side  ^rav^  C 

SeclioTV  cf  Chatrnet  a?  ^ 


CJ^armelT'u^ih  iron  p-raTf  /5ec?«bw  cf  cfntre  proves  2> 

•Sections  of  the  various  Parts  of  the  Stable  Floors 

SHOWN  on  Illustration 
NO.  4.  NO.  5. 


Concrete  Slab  Moulds. — Slab  moulds  are  made  With 
iy2  inch  boards  ledged  together.  On  this  ground,  wood 
sides  and  ends  (each  being  21/^  inches  by  2  inches,  or  3 
inches  by  3  inches,  according  to  the  desired  thickness  of 
slab)  are  fixed.  One  side  and  end  is  held  in  position 
with  thumb  screws,  which  fit  into  iron  sockets,  so  that 
they  can  be  unscrewed  to  relieve  the  slab  when  set.  The 
bottom  and  the  sides  and  ends  are  lined  with  strong  iron 
or  zinc  plates. 


330 


CEMENTS  AND  CONCRETES 


Slab  Making. — Slabs  are  mostly  made  by  machinery. 
The  materials  are  1  part  of  Portland  cement  mixed  dry 
with  2%  parts  of  crushed  granite  and  slag  in  equal  pro- 
portions that  have  been  washed  and  passed  through  a  % 
inch  sieve.  They  are  thoroughly  incorporated  together 
in  a  horizontal  cylinder  worked  by  machinery,  a  mini- 
mum of  water  being  added,  and  the  mixing  continued 
until  the  mass  is  well  gauged.  The  mould,  which  has 
been  previously  oiled,  is  placed  on  a  shaking  machine 
known  as  a  ^  ^  trembler ' '  or  ^  ^  dither, ' '  which  gives  a  rapid 
vertical  jolting  motion  to  the  mould  and  its  contents.  A 
small  portion  of  ^'slip,"  that  is,  neat  cement,  is  laid 
round  the  angles.  The  machine  is  then  started,  and  the 
concrete  laid  on  the  mould  by  small  shovelfuls  at  a  time, 
a  man  with  a  trowel  spreading  it  over  the  mould  until 
full.  The  surface  is  then  ruled  off.  If  both  sides  of  the 
slabs  are  required  for  use,  the  upper  surface  is  trowelled. 
The  whole  operation  of  mixing,  filling  in,  and  ruling  off 
takes  about  seven  minutes.  The  filled  moulds  are  re- 
moved and  allowed  to  stand  for  about  three  days.  The 
slabs  are  then  taken  out,  and  stacked  on  edge  and  air- 
dried  for  about  five  days.  They  are  then  immersed  in 
a  silicate  bath  for  about  seven  days,  and  are  afterwards 
taken  out  and  stacked  in  the  open  air  until  it  is  required 
for  use.  They  should  not  be  used  until  three  months 
old.  Paving  slabs  are  also  made  by  hand,  by  ramming 
and  beating  the  moist  concrete  into  the  mould  with  an 
iron  hand-float.  Powerful  ramming,  trituration,  or  vio- 
lent agitation  of  the  gauged  material  in  the  mould,  tend 
to  consolidate  concrete,  and  it  is  possible  to  further  in- 
crease homogeneity  by  the  use  of  hydraulic  pressure. 

Induration  Concrete  Slabs. — The  surface  of  concrete 
slabs  or  other  work  exposed  to  friction  or  wear  may  be 


HOW  TO  use;  them 


331 


hardened  by  soaking  in  a  silicate  solution.  Silicate  of 
soda  has  a  great  affinity  for  the  materials  of  which  con- 
crete is  composed,  and  by  induration  causes  the  surface 
to  become  hard,  dense,  and  non-porous. 

The  silicate  of  soda  and  potash  is  known  as  soluble 
glass  or  dissolved  flint.  The  soluble  silicate  is  a  clear 
viscous  substance  made  from  pure  flint  and  caustic  soda, 
which  is  digested  by  heat  under  pressure  indigester.  Its 
strength  is  technically  known  as  140  degrees,  which 
shows  1,700  on  a  hygrometer.  When  used  as  a  bath  for 
concrete,  it  is  diluted  with  water,  the  proportion  vary- 
ing from  6  to  10  parts  of  water  to  one  of  silicate.  Con- 
crete pavements,  laid  in  situ,  may  also  be  hardened  by 
washing  with  silicate  solution.  They  should  not  be  sili- 
cated  until  two  days  after  being  laid,  to  allow  the  mois- 
ture to  evaporate  and  the  silicate  to  penetrate. 

Mosaic, — The  art  of  making  mosaic  is  at  the  present 
time  scarcely  within  the  province  of  plasterers,  but  in 
former  times  many  kinds  were  made  in  situ  or  in  slabs 
by  plasterers.  The  subdivision  of  labor  has  to  a  great 
extent  caused  mosaic-making  to  be  conflned  to  special- 
ists. Concrete  is  still  made  by  plasterers.  A  brief  de- 
scription of  this  and  other  kinds  may  prove  useful  as 
well  as"  interesting,  especially  to  plasterers  who  are  in 
the  habit  of  fixing  tiles  and  working  in  concrete.  Mosaic 
is  the  art  of  producing  geometrical,  floral,  or  figured  de- 
signs, by  the  joining  together  of  hard  stones,  marbles, 
earthenware,  glass,  or  artificial  stone,  either  naturally 
or  artificially  colored.  The  term  ^ ^mosaic''  embraces  a 
wide  range  of  artistic  processes  and  materials  for  the 
decoration  of  floors,  walk,  ceilings.  The  Egyptians  were 
experts  in  mosaic.  The  Cairo  worker  as  a  rule  had  no 
drawings  made  beforehand,  but  the  mosaic  design  was 


332 


CEMENTS  AND  CONCRETES 


constructed  by  the  artist  as  he  arranged  the  pieces  on 
the  ground.  The  mosaic  pavements  of  Cairo  are  of  a 
slightly  different  character  from  those  used  for  wall 
decoration,  and  are  generally  composed  entirely  of  mar- 
ble tesserae  (and  sometimes  red  earthenware)  of  larger 
size  than  the  delicate  pieces  included  in  wall  mosaics. 
They  are  arranged  to  form  geometrical  patterns  within 
a  space  of  about  two  feet  square.  Each  square  slab  is 
made  separately,  and  the  pieces  are  set,  not  in  plaster, 
but  in  a  composition  of  lime  and  clay  impervious  to 
water.  The  clay  must  be  unbumt,  just  as  it  comes  from 
the  pit.  Saracenic  mosaic  in  Egypt  is  a  combination  of 
the  tesselated  method  with  a  large  proportion  of  sectile 
mosaic.  The  Romans  also  were  great  workers  in  mosaic. 
The  mosaics  of  Byzantium  and  Ravenna  consisted  of 
cubes  of  opaque  and  colored  glass.  ,  % 

The  general  method  used  here  for  pavement  mosaic  is 
as  follows :  The  repeated  design  is  traced  on  stout  paper 
and  small  pieces  of  marble,  or  more  often  tile,  are 
gummed  on  the  paper,  following  the  design  of  form  and 
color,  one  piece  at  a  time  (with  the  smooth  face  down- 
wards) being  laid  until  the  design  is  completed.  The 
mosaic  slabs,  which  are  thus  temporarily  kept  in  posi- 
tion, are  sent  to  the  building  and  laid  where  intended. 
A  rough  concrete  foundation,  which  has  previously  been 
made  level,  is  then  floated  with  Portland  or  Keen's 
cement,  and  the  slabs  with  paper  are  then  damped  and 
drawn  off,  and  any  openings  or  defects  filled  up  with 
small  pieces  of  the  same  form  and  color  as  the  design. 
The  slabs  are  made  in  various  sizes  according  to  the  de- 
sign. For  instance,  a  border  12  inches' wide  may  be  made 
from  3  to  6  inches  long.  When  laying  the  slabs,  it  is  best 
to  begin  at  the  centre  and  work  outwards,  and  any  ex- 


HOW  TO  USE  THEM 


333 


cess  or  deficiency  taken  off  or  made  up  in  the  plain  part 
of  the  border  at  the  walls.  The  tiles  are  made  at  pottery 
works  in  the  required  sizes  and  colors.  The  thickness  is 
generally  about  i/4  i^ch  and  the  average  surface  size 
about  %  inch.  Females  are  often  employed  fixing  the 
pieces  on  the  paper.  The  designs  of  coats  of  arms,  mono- 
grams, dates,  figures,  flowers,  and  foliage  are  effectively 
produced  by  this  simple  and  cheap  process. 

Concrete  Mosaic. — All  mosaics  are  more  or  less  of  a 
concretive  nature,  and  the  trade  term  of  concrete  mo- 
saic" is  due  to  the  fact  that  the  matrix  used  is  Portland 
or  other  cement  gauged  with  -the  marble  aggregate,  and 
laid  in  most  cases  in  a  similar  manner  as  ordinary  con- 
crete. Concrete  mosaic  is  extensively  used  for  paving 
halls,  corridors,  conservatories,  terraces,  &c.  It  is  also 
used  for  constructing  steps,  landings,  baths,  pedestals, 
&c.  Slabs  and  tiles  made  of  this  class  of  mosaic  for 
paving  purposes  are  slowly  but  surely  proving  a  for- 
midable rival  to  Italian  mosaic  encaustic  tiles.  It  can 
be  made  in  larger  sections,  thus  facilitating  rapidity  of 
laying.  It  is  more  accurate  in  form^  durable,  non-slip- 
pery, and  cheaper.  The  last  reason  alone  is  a  faVorable 
item  in  this  keen  age  of  competition.  Where  marble  has 
been  scarce,  broken  tiles,  pottery,  colored  glass,  flints, 
white  spar,  &c.,  have  been  used  as  aggregate.  If  the 
marble  chips  are  obtainable  as  a  waste,  and  near  the  place 
of  manufacture,  the  primary  cost  is  small.  If  the  moulds 
are  of  metal,  and  made  in  sections  so  as  to  form  a  series 
of  moulds  in  one  case,  and  the  casts  are  pressed  by  means 
of  a  hydraulic  power,  the  cost  of  production  is  reduced 
to  a  minimum.  If  the  casts  are  polished  in  large  num- 
bers by  machinery  on  a  revolving  table,  the  total  cost  is 
further  reduced.    For  local  purposes  they  can  be  made 


334  CEMENTS  AND  CONCRETES 


by  hand  at  a  medium  cost.  Slabs  are  made  in  almost 
any  size,  but  generally  from  4  to  6  feet  superficial.  The 
thickness  varies  from  1  to  l^/^  inches.  Tiles  are  usually 
made  about  10  inches  square  and  1  inch  thick.  The  tiles 
are  generally  made  with  a  face  of  cement  and  white  mar- 
ble, or  white  and  black  marble  chippings.  They  are 
backed  up  with  a  cheaper  aggregate.  Various  tints  of 
the  face  matrix  are  obtained  by  mixing  the  cement  with 
metallic  ovides.  The  tiles  are  made  in  wood  or  metal 
moulds,  with  metal  strips  to  form  the  divisions  of  form 
and  color  in  the  design.  If  the  design  is  fret  pattern, 
the  gauged  material  is  put  in  between  the  strips  that 
form  the  band  of  the  fret.  When  the  stuff  is  nearly  set, 
the  strips  are  taken  out,  and  the  other  part  filled  in  with 
another  color.  Sometimes  the  band  or  running  designs 
are  cast  in  a  separate  mould,  and  when  set  placed  in  posi- 
tion in  a  larger  mould,  and  the  ground  filled  in,  cover- 
ing and  binding  the  whole  in  one  tile.  Another  plan  is 
to  lay  a  thin  coat  of  cement  on  the  face  of  the  mould, 
forming  the  design  with  small  marble  chips  by  hand,  by 
pressing  the  marble  into  the  cement  as  desired.  When 
it  is  firm,  it  is  backed  up  with  the  ordinary  stuff,  and 
when  set,  they  are  ground  and  polished. 

Concrete  Mosaic  Laid  ''in  Sihi.^^ — Pavements  for 
halls,  passages,  shops,  landings,  &c.,  are  also  done  in  situ. 
A  rough  concrete  foundation  is  first  laid  fair  to  falls 
and  levels  within  %  inch  of  the  finished  surface  line. 
This  %  inch  space  is  to  receive  the  plastic  marble  mo- 
saic. The  main  or  centre  part  is  generally  done  first 
and  the  border  last.  This  allows  a  walking  space  or 
bearing  for  boards,  laid  from  side  to  side  to  work  on 
when  laying  the  centre.  A  plank  sufficiently  strong  to 
keep  one  or  two  crossboards  from  touching  the  work  is 


HOW  TO  USE  THEM 


335 


laid  along  each  side.  On  the  side  planks  the  crossboards 
are  laid,  and  moved  about  when  required.  The  width  of 
the  border  is  marked  on  the  floor,  and  wood  screed  rules 
laid  level  to  the  marks  to  form  a  fair  joint  line  for  the 
border,  also  as  a  screed  when  floating  the  centre  part. 
The  screed  rules  are  generally  fixed  with  a  gauge  plaster, 
which  is  quicker  than  fixing  on  gauged  cement.  After 
the  centre  is  laid,  the  plaster  should  be  carefully  swept 
off,  and  the  concrete  well  wetted  before  the  border  is  laid. 
The  marble  and  cement  is  gauged  in  the  proportion  of  2 
of  marble  to  1  of  cement,  and  laid  flush  with  screeds, 
laying  and  beating  it  in  position  with  a  long  wood  hand- 
float.  The  surface  is  ruled  in  from  screed  to  screed  with 
a  straight-edge.  The  surface  is  then  ironed  with  a  lay- 
ing trowel  until  it  is  smooth  and  fair.  If  the  marble 
does  not  show,  or  is  not  regular,  or  is  insufficient,  the 
bare  parts  are  filled  in  with  marble  by  hand.  When 
marble  is  scarce,  the  %  inch  of  the  top  surface  is  laid  in 
two  coats,  the  first  being  composed  of  cement  and  a 
cheaper  aggregate,  such  as  broken  stone,  tiles,  &c.,  and 
gauged  in  the  same  proportion  as  the  upper  or  marble 
coat.  It  is  laid  about  i/4  ^^ch  thick,  and  when  it  is  firm, 
but  not  set,  the  marble  coat  is  laid  as  before  directed. 
The  first  coat  saves  the  marble,  and  being  firm,  tends  to 
keep  the  marble  in  the  upper  coat  from  sinking.  The 
top  coat  is  sometimes  sprinkled  over  with  fine  marble 
chips  by  hand  or  through  a  fine  sieve,  then  pressed  into 
the  surface  and  ironed  with  a  laying  trowel.  Before 
ironing  the  surface,  care  should  be  taken  that  the  chips 
are  equally  distributed,  also  that  their  fiat  surfaces  are 
uppermost,  and  that  the  matrix  and  chips  are  perfectly 
solid  and  free  from  ridges  and  holes.  After  the  centre 
is  laid  and  the  screeds  removed,  the  border  is  laid  in  a 


336  CEMENTS  AND  CONCRETES 


similar  way.  If  there  are  two  or  more  colors  or  forms  in 
the  border,  the  divisions  are  formed  with  narrosv  screed 
rules,  and  arranged  so  that  as  many  as  practicable  can 
be  laid  at  the  same  time.  This  allows  the  various  parts 
to  set  at  one  time,  and  saves  waiting  for  each  separate 
part  to  set.  The  screed  rules  for  circular  work  or  angles 
are  formed  with  strong  gauged  plaster  and  then  oiled. 

The  marble  chips  are  either  broken  by  hand  or  in  a 
stone-breaking  machine.  The  chips  vary  in  size  from 
1-10  to  l^  inch.  The  best  colors  for  borders  are  a  black 
matrix  with  white  marble  or  spar  chips,  or  a  white 
matrix  with  black  marble  chips.  The  white  matrix  is 
obtained  by  mixing  the  marble  dust  (produced  when 
breaking  the  marble  into  chips)  with  a  light  colored 
Portland  cement.  The  centres  can  be  made  in  various 
tints,  but  the  most  general  is  a  w^arm  red,  which  is  ob- 
tained by  mixing  the  cement  with  red  oxide.  Cement 
colored  with  red  oxide  should  be  laid  first,  as  it  is  liable 
to  stain  other  parts  of  a  lighter  color.  When  the  centre 
and  border  are  laid,  the  floor  is  left  until  the  whole  is 
perfectly  set  and  hard,  and  it  is  then  fit  to  polish.  This 
is  done  by  means  of  a  stone  polisher,  water  and  marble 
dust,  or  fine  slag  powder.  The  stone  polisher  is  a  piece 
of  hard  stone  from  8  to  12  inches  square,  and  about  3 
inches  thick,  into  which  an  iron  ring  is  inserted  and  se- 
cured with  lead.  A  wooden  handle  from  4  to'  6  feet  long, 
with  an  iron  hook  at  one  end,  is  inserted  into  the  ring, 
so  that  the  handle  is  firm  on  the  stone,  yet  has  sufficient 
play  to  be  moved  freely  backwards  and  forwards.  The 
polishing  should  not  be  attempted  until  the  stuff  is  thor- 
oughly set,  because  the  polishing  will  destroy  the  face 
of  the  cement,  and  cause  a  vast  amount  of  extra  labor  in 
grinding  the  surface  down  until  free  from  holes.  Small 


HOW  TO  USE  THEM 


337 


parts  of  the  gauged  stuff  should  be  set  aside  as  tests  for 
determining  when  the  stuff  is  set.  Concrete  mosaic, 
where  economy  is  desirable,  will  make  a  strong,  durable, 
and  waterproof  floor,  and  an  excellent  substitute  for 
higher  class  mosaics. 

A  Bulletin  (No.  235),  prepared  by  P.  S.  Wormley  for 
the  U.  S.  government  on  cement,  mortar,  and  concrete, 
from  which  I  quote  at  length,  contains  some  excellent  in- 
formation and  instructions  on  the  preparation  and  the 
use  of  the  above  materials.  This  bulletin  is  intended  for 
free  distribution  and  may  be  obtained  by  making  appli- 
cation to  the  U.  S.  Department  of  Agriculture,  Wash- 
ington, D.  C. 

Storing  Cement. — In  storing  cement  care  must  be  ex- 
ercised to  insure  its  being  kept  dry.  When  no  house  or 
shed  is  available  for  the  purpose,  a  rough  platform  may 
be  erected  clear  of  the  ground^  on  which  the  cement  may 
be  placed  and  so  covered  as  to  exclude  water.  When 
properly  protected,  it  often  improves  with  age.  Cement 
is  shipped  in  barrels  or  bags,  the  size  and  weight  of 
which  usually  are  given. 

Cement  Mortar. — Cement  mortar  is  an  intimate  mix- 
ture of  cement  and  sand  mixed  with  sufficient  water  to 
produce  a  plastic  mass.  The  amount  of  water  will  vary 
according  to  the  proportion  and  condition  of  the  sand, 
and  had  best  be  determined  independently  in  each  case. 
Sand  is  used  both  for  the  sake  of  economy  and  to  avoid 
cracks  due  to  shrinkage  of  cement  in  setting.  Where 
great  strength  is  required,  there  should  be  at  least  suffi- 
cient cement  to  fill  the  voids  or  air  spaces  in  the  sand, 
and  a  slight  excess  is  preferable  in  order  to  compensate 
for  any  uneven  distribution  in  mixing.  Common  propor- 
tions for  Portland  cement  mortar  are  3  parts  sand  to  1 


338  CEMENTS  AND  CONCRETES 

of  cement,  and  for  natural  cement  mortar,  2  parts  sand 
to  1  of  cement.  Unless  otherwise  stated,  materials  for 
mortar  or  concrete  are  considered  to  be  proportioned  by 
volume,  the  cement  being  slightly  shaken  in  the  measure 
used. 

A  ''lean''  mortar  is  one  having  only  a  small  propor- 
tion of  cement,  while  a  ''rich''  mixture  is  one  with  a 
large  proportion  of  cement.  "Neat"  cement  is  pure 
cement,  or  that  with  no  admixture  of  sand.  The  term 
' '  aggregate ' '  is  used  to  designate  the  coarse  materials  en- 
tering into  concrete — usually  gravel  or  crushed  rock. 
The  proportion  in  which  the  three  elements  enter  into 
the  mixture  is  usually  expressed  by  three  figures  sepa- 
rated by  dashes — as,  for  instance,  1-2-5,  meaning  1  part 
cement,  2  parts  sand,  and  5  parts  aggregate.  In  the 
great  majority  of  cases  cement  mortar  is  subjected  only 
to  compression,  and  for  this  reason  it  would  seem  nat- 
ural that,  in  testing  it,  to  determine  its  compressive 
strength.  The  tensile  strength  of  cement  mortar,  how- 
ever, is  usually  determined,  and  from  this  its  resistance 
to  compression  may  be  assumed  to  be  from  8  to  12  times 
greater.  A  direct  determination  of  the  compressive 
strength  is  a  less  simple  operation,  for  which  reason  the 
tensile  test  is  in  most  cases  accepted  as  indicating  the 
strength  of  the  cement. 

Mixing. — In  mixing  cement  mortar  it  is  best  to  use  a 
platform  of  convenient  size  or  a  shallow  box.  First,  de- 
posit the  requisite  amount  of  sand  in  a  uniform  layer, 
and  on  top  of  this  spread  the  cement.  These  should  be 
mixed  dry  with  shovels  or  hoes,  until  the  whole  mass  ex- 
hibits a  uniform  color.  Next,  form  a  crater  of  the  dry 
mixture,  and  into  this  pour  nearly  the  entire  quantity  of 
water  required  for  the  batch.    Work  the  dry  material 


HOW  TO  USE  THEM 


339 


from  the  outside  toward  the  centre,  until  all  the  water 
is  taken  up,  then  turn  rapidly  with  shovels,  adding  water 
at  the  same  time  by  sprinkling  until  the  desired  consist- 
ency is  attained.  It  is  frequently  specified  that  the  mor- 
tar shall  be  turned  a  certain  number  of  times^  but  a  bet- 
ter practice  for  securing  a  uniform  miixture  is  to  watch 
the  operation  and  judge  by  the  eye  when  the  mixing  has 
been  carried  far  enough.  In  brick  masonry  the  mis- 
take is  frequently  made  of  mixing  the  mortar  very  wet 
and  relying  upon  the  bricks  to  absorb  the,  excess  of 
water.  It  is  better,  however,  to  wet  the  brick  thoroughly 
and  use  a  stiff  mortar. 

Grout. — The  term  ''grouf  is  applied  to  mortar  mixed 
with  an  excess  of  water,  which  gives  about  the  consist- 
ency of  cream.  This  material  is  often  used  to  fill  the 
voids  in  stone-masonry^  and  in  brick  work  the  inner  por- 
tions of  walls  are  frequently  laid  dry  and  grouted.  The 
practice  in  either  case  is  to  be  condemned,  except  where 
the  conditions  are  unusual,  as  cement  used  in  this  way 
will  never  develop  its  full  strength. 

Lime  and  Cement  Mortar. — L.  C.  Sabin  finds  that  in 
Portland  cement  mortar  containing  three  parts  sand  to 
1  of  cement,  10  per  cent,  of  the  cement  may  be  replaced 
by  lime  in  the  form  of  paste  without  diminishing  the 
strength  of  the  mortar,  and  at  the  same  time  rendering  it 
more  plastic.  In  the  case  of  natural  cement  mortar,  lime 
may  be  added  to  the  extent  of  20  to  25  per  cent,  of  the 
cement  with  good  results.  The  increased  plasticity  due 
to  the  addition  of  lime  much  facilitates  the  operation  of 
laying  bricks,  and  has  caused  lime  and  cement  mortar  to 
be  largely  used. 

Cement  Mortar  for  Plastering. — In  plastering  with 
cement^  a  few  precautions  must  be  observed  to  insure 


340  CEMENTS  AND  CONCRETES 


good  and  permanent  results.  The  surface  to  receive  the 
plaster  should  be  rough,  perfectly  clean,  and  well  satu- 
rated with  water.  A  mortar  very  rich  in  cement  is 
rather  a  drawback  than  otherwise  on  account  of  shrink- 
age cracks,  which  frequently  appear.  The  mortar,  con- 
sisting of  two  or  three  parts  sand  to  one  of  cement, 
should  be  mixed  with  as  litt4e  water  as  possible  and  well 
worked  to  produce  plasticity.  It  is  essential  that  the 
plaster  be  kept  moist  until  it  has  thoroughly  hardened. 

Materials  for  Making  Concrete  Sand, — In  securing 
sand  for  mixing  mortar  or  concrete,  if  it  is  possible  to 
select  from  several  varieties,  that  sand  should  be  chosen 
which  is  composed  of  sharp,  angular  grains,  varying  in 
size  from  coarse  to  fine.  Such  sand  is,  however,  not 
always  obtainable,  nor  is  it  essential  for  good  work.  Any 
coarse-grained  sand  which  is  fairly  clean  will  answer 
the  purpose.  If  gravel,  sticks,  or  leaves  be  present  they 
should  be  removed  by  screening.  The  voids  in  sand  vary 
from  30  to  40  per  cent.,  according  to  the  variation  in 
size  of  grains.  A  sand  with  different-sized  grains  is  to 
be  preferred,  because  less  cement  is  required  to  fill  the 
voids.  By  mixing  coarse  and  fine  sand  it  is  possible  to 
reduce  the  voids  considerably. 

It  is  customary  to  use  the  terms  river  sand,''  ^^sea 
sand,''  or  ^^pit  sand,"  according  to  the  source  of  the 
supply.  River  sand  as  a  rule  has  rounded  grains,  but 
unless  it  contains  an  excess  of  clay  or  other  impurities,  it 
is  suitable  for  general  purposes.  When  river  sand  is  of 
a  light  color  and  fine-grained  it  answers  well  for  plaster- 
ing. 

Sea  sand  may  contain  the  salts  found  in  the  ocean. 
The  tendency  of  these  salts  to  attract  moisture  makes  it 


HOW  TO  USE  THEM 


341 


advisable  to  wash  sea  sand  before  using  it  for  plastering 
or  other  work  which  is  to  be  kept  perfectly  dry. 

Pit  sand  for  the  most  part  will  be  found  to  have 
sharp,  angular  grains,  which  make  it  excellent  for  mor- 
tar or  concrete  work.  Where  clay  appears  in  pockets  it 
is  necessary  either  to  remove  it,  or  else  see  that  it  is 
thoroughly  mixed  with  the  sand.  The  presence  of  gIslj  in 
excess  frequently  makes  it  necessary  to  wash  pit  sand 
before  it  is  suitable  for  use. 

The  results  of  tests  made  in  this  laboratory  would  in- 
dicate that  the  presence  of  clay,  even  in  considerable 
amounts,  is  a  decided  benefit  to  ' '  lean ' '  mortars,  whereas 
it  does  not  appreciably  affect  the  strength  of  a  rich 
mixture. 

Gravel, — It  is  important  that  gravel  for  use  in  con- 
crete should  be  clean,  in  order  that  the  cement  may  prop- 
erly adhere  to  it,  and  form  a  strong  and  compact  mass. 
As  with  sand,  it  is  well  to  have  the  pieces  vary  in  size, 
thereby  reducing  the  voids  to  be  filled  with  mortar.  The 
voids  in  general  range  from  35  to  40  per  cent. 

Crushed  Stone. — The  best  stone  for  concrete  work  con- 
sists of  angular  pieces,  varying  in  size  and  having  a 
clean,  rough  surface.  Some  form  of  strong  and  durable 
rock  is  to  be  preferred,  such  as  limestone,  trap,  or  gran- 
ite. The  total  output  of  the  crusher  should  be  used  be- 
low a  maximum  size,  depending  upon  the  nature  of  the 
work  in  hand.  All  material  under  %  inch  will  act  as  so 
much  sand  and  should  be  considered  as  such  in  propor- 
tioning the  mixture.  Precautions  must  be  taken  to  in- 
sure a  uniform  distribution  of  the  smaller  pieces  of  stone, 
otherwise  the  concrete  will  have  an  excess  of  fine  ma- 
terial in  some  parts  and  a  deficiency  in  others. 


342 


CEMENTS  AND  CONCRETES 


Less  than  8  per  cent,  of  clay  will  probably  not  seri- 
ously impair  the  strength  of  the  concrete,  provided  the 
stones  are  not  coated  with  it,  and  may  even  prove  a 
benefit  in  the  case  of  lean  mixtures.  The  voids  in  crushed 
stone  depend  upon  the  shape  and  variation  in  size  of 
pieces,  rarely  falling  below  40  per  cent.,  unless  much 
fine  material  is  present,  and  in  some  cases  reaching  50 
per  cent.  A  mixture  of  stone  and  gravel  in  equal  parts 
makes  an  excellent  aggregate  for  concrete. 

Stone  Versus  Gravel, — It  would  appear  from  tests  that 
crushed  stone  makes  a  somewhat  stronger  concrete  than 
gravel,  but  the  latter  is  very  extensively  used  with  uni- 
formly good  results.  This  superiority  of  stone  over 
gravel  for  concrete  work  is  attributed  to  the  fact  that  the 
angular  pieces  of  stone  interlock  more  thoroughly  than 
do  the  rounded  pebbles,  and  offer  a  rougher  surface  to 
the  cement.  A  point  in  favor  of  gravel  concrete  is  that 
it  requires  less  tamping  to  produce  a  compact  mass  than 
in  the  case  of  crushed  stone.  Then,  too,  the  proportion 
of  voids  in  stone  being  usually  greater  than  in  gravel, 
means  a  slight  increase  in  the  cost  of  concrete. 

Cinders. — Cinders  concrete  is  frequently  used  in  con- 
nection with  expanded  metal  and  other  forms  of  rein- 
forcement for  floor  construction,  and  for  this  purpose  it 
is  well  adapted  on  account  of  its  light  weight.  Its  poros- 
ity makes  it  a  poor  conductor  of  heat  and  permits  the 
driving  of  naik.  Only  hard  and  thoroughly  burned  cin- 
ders should  be  used,  and  the  concrete  must  be  mixed 
quite  soft  so  as  to  require  but  little  tamping  and  to  avoid 
crushing  the  cinders.  Cinder  concrete  is  much  weaker, 
both  in  tension  and  compression,  than  stone  or  gravel 
concrete,  and  for  this  reason  admits  only  of  light  rein- 
forcement. 


HOW  TO  USE  THEM 


343 


Concrete. — General  Discussion :  Cement  concrete  is 
the  product  resulting  from  an  intimate  mixture  of 
cement  mortar  with  an  aggregate  of  crushed  stone, 
gravel,  or  similar  material.  The  aggregate  is  crushed  or 
screened  to  the  proper  size  as  determined  from  the  char- 
acter of  the  work.  In  foundation  work,  stone  or  gravel 
3  inches  in  size  may  be  used  to  advantage,  whereas  in  the 
case  of  moulded  articles  of  small  sectional  area,  such  as 
fence  posts,  hollow  building  blocks,  &c.,  it  is  best  to  use 
only  such  material  as  will  pass  a  I/2  inch  screen.  An 
ideal  concrete,  from  the  standpoint  of  economy,  would 
be  that  in  which  all  voids  in  the  aggregate  were  com- 
pletely filled  with  sand,  and  all  the  voids  in  the  sand 
completely  filled  with  cement,  without  any  excess.  Un- 
der these  conditions  there  would  be  a  thoroughly  com- 
pact mass  and  no  waste  of  materials. 

It  is  a  simple  matter  to  determine  the  voids  in  sand 
and  also  in  the  aggregate,  but  in  mixing  concrete  the 
proportions  vary  a  great  deal,  depending  in  each  case 
upon  the  nature  of  the  work  and  the  strength  desired. 
For  example,  in  the  construction  of  beam??  and  flour  pan- 
els, where  maximum  strength  with  minimum  weight  is 
desired,  a  rich  concrete  should  be  used,  whereas  in  mas- 
sive foundation  work,  in  which  bulk  or  weight  is  the 
controlling  factor,  economy  would  point  to  a  lean  mix- 
ture. When  good  stone  or  gravel  is  used,  the  strength  of 
the  concrete  depends  upon  the  strength  of  the  mortar  em- 
ployed in  the  mixing  and  the  proportion  of  mortar  to 
aggregate.  For  a  given  mortar  the  concrete  will  be 
strongest  when  only  enough  mortar  is  used  to  fill  the 
voids  in  the  aggregate,  less  strength  being  obtained  by 
using  either  greater  or  less  proportion.   In  practice  it  is 


344 


CEMENTS  AND  CONCRETES 


usual  to  add  a  slight  excess  of  mortar  over  that  required 
to  fill  the  voids  in  the  aggregate. 

It  is  more  accurate  to  measure  cement  by  weight  un- 
less the  unit  employed  be  the  barrel  or  sack,  because 
when  taken  from  the  original  package  and  measured  in 
bulk  there  is  a  chance  of  error  due  to  the  amount  of 
shaking  the  cement  receives.  As  it  is  less  convenient, 
however,  to  weigh  the  cement,  it  is  more  usual  to 
measure  it  by  volume,  but  for  the  reasons  stated  this 
should  be  done  with  care. 

Proportioning  Materials. — For  an  accurate  determina- 
tion of  the  best  and  most  economical  proportions  where 
maximum  strength  is  required,  it  is  well  to  proceed  in 
the  following  way:  First,  proportion  the  cement  and 
sand  so  that  the  cement  paste  will  be  100  per  cent,  in  ex- 
cess of  the  voids  in  sand;  next,  determine  the  voids  in 
the  aggregate  and  allow  sufficient  mortar  to  fill  all  voids, 
with  an  excess  of  10  per  cent. 

To  determine  roughly  the  voids  in  gravel  or  crushed 
stone  prepare  a  water-tight  box  of  convenient  size  and 
fill  with  the  material  to  be  tested,  shake  well  and  smooth 
off  even  with  the  top.  Into  this  pour  water  until  it  rises 
flush  with  the  surface.  The  volume  of  water  added, 
divided  by  the  volume  of  the  box,  measured  in  the  same 
units,  represents  the  proportion  of  voids.  The  propor- 
tion of  voids  in  sand  may  be  more  accurately  determined 
by  subtracting  the  weight  of  a  cubic  foot  of  packed  sand 
from  165,  the  weight  of  a  cubic  foot  of  quartz,  and  divid- 
ing the  difference  by  165  degrees. 

The  following  will  serve  as  an  example  of  proportion- 
ing materials:  Assume  voids  in  packed  sand  to  measure 
38  per  cent.,  and  voids  in  packed  stone  to  measure  48 
per  cent.   Cement  paste  required  per  cubic  foot  of  sand, 


HOW  TO  USE  THEM 


345 


0.38  and  1-10  equals  0.42  cubic  foot,  approximately.  By 
trial,  1  cubic  foot  of  loose  cement,  lightly  shaken,  makes 

0.85  cubic  foot  of  cement  paste,  and  requires  or 
2  cubic  feet  of  sand,  approximately,  producing  an 
amount  of  mortar  equal  to  0.85  and  2  (1-0.38)  equals 
2.09  cubic  feet.  Mortar  required  per  cubic  foot  of  stone 
equals  0.48,  and  1-10x0.48  equals  0.528  cubic  foot.  There- 
fore 2.09  cubic  feet  mortar  will  require  equals 
4  cubic  feet  of  stone,  approximately.  The  proportions 
are  therefore  1  part  cement,  2  parts  sand,  4  parts  stone. 
Although  such  a  determination  is  usually  considered  un- 
necessary in  practical  work,  it  may  be  of  sufficient  inter- 
est to  justify  giving  it. 

For  general  use  the  following  mixtures  are  recom- 
^  mended :  1  cement,  2  sand,  4  aggregate,  for  very  strong 
and  impervious;  1  cement,  2%  sand,  5  aggregate,  for 
ordinary  work  requiring  moderate  strength ;  1  cement,  3 
sand,  6  aggregate,  for  work  where  strength  is  of  minor 
importance. 

Aggregate  Containing  Fine  Material. — In  the  case  of 
gravel  containing  sand,  or  crushed  stone  from  which  the 
small  articles  have  not  been  removed  by  screening,  the 
amount  of  such  fine  sand  or  fine  stone  should  be  deter- 
mined and  due  allowance  made  for  it  in  proportioning 
the  mortar. 

When  mixing  an  aggregate  containing  small  particles 
with  mortar,  and  in  reality  we  have  a  mortar  containing 
a  larger  proportion  of  sand  than  was  present  before  the 
aggregate  was  incorporated.  It  is  evident,  then,  that  in 
such  cases  the  quality  of  richness  of  the  mortar  should 
depend  upon  the  proportion  of  fine  material  in  the  ag- 
gregate. 


346 


CEMENTS  AND  CONCKETES 


For  example,  suppose  that  1  cubic  foot  of  gravel  con- 
tains 0.1  cubic  foot  of  sand,  and  that  the  voids  in  gravel 
with  sand  screened  out  measure  40  per  cent.  For  gen- 
eral purposes  this  would  suggest  a  1-2-5  mixture,  but 
since  each  cubic  foot  contains  0.1  cubic  foot  sand;  5 
cubic  feet  gravel  will  contain  0.5  cubic  foot  sand,  and 
the  proportions  should  be  changed  to  1  part  cement,  1^ 
parts  sand,  5  parts  gravel. 

Mechanical  Mixers. — It  has  been  demonstrated  that 
concrete  can  be  mixed  by  machinery  as  well,  if  not  bet- 
ter, than  by  hand.  Moreover,  if  large  quantities  of  con- 
crete are  required,  a  mechanical  mixer  introduces  marked 
economy  in  the  cost  of  construction.  None  of  the  various 
forms  of  mechanical  mixers  will  be  described  here,  since 
concrete  in  small  quantities,  as  would  be  used  on  the 
farm,  is  more  economically  mixed  by  hand. 

Mixing  by  Hand. — In  mixing  by  hand  a  platform  is 
constructed  as  near  the  work  as  is  practicable,  the  sand 
and  aggregate  being  dumped  in  piles  at  the  side.  If  the 
work  is  to  be  continuous,  this  platform  should  be  of  suf- 
ficient size  to  accommodate  two  batches,  so  that  one  batch 
can  be  mixed  as  the  other  is  being  deposited.  The  ce- 
ment must  be  kept  under  cover  and  well  protected  from 
moisture.  A  convenient  way  of  measuring  the  materials 
is  by  means  of  a  bottomless  box  or  frame  made  to  hold 
the  exact  quantities  needed  for  a  batch. 

A  very  common  and  satisfactory  method  of  mixing 
concrete  is  as  follows:  First  measure  the  sand  and  ce- 
ment required  for  a  batch  and  mix  these  into  mortar  as 
described  on  page  5.  Spread  out  this  mortar  in  a  thin 
layer  and  on  top  of  it  spread  the  aggregate,  which  has 
been  previously  measured  and  well  wetted.  The  mixing 
is  done  by  turning  with  shovels  three  or  more  times,  as 


HOW  TO  USE  THEM 


347 


may  be  found  necessary  to  produce  a  thoroughly  uni- 
form mixture,  water  being  added  if  necessary  to  give 
the  proper  consistency.  The  mixers,  two  or  four  in  num- 
ber, according  to  the  size  of  the  batch,  face  each  other 
and  shovel  to  right  and  left,  forming  two  piles,  after 
which  the  material  is  turned  back  into  a  pile  at  the  cen- 
tre. By  giving  the  shovel  a  slight  twist,  the  material  is 
scattered  in  leaving  it  and  the  efficiency  of  the  mixing 
is  much  increased. 

Consistency  of  Concrete. — A  dry  mixture,  from  which 
water  can  be  brought  to  the  surface  only  by  vigorous 
tamping,  is  probably  the  strongest,  but  for  the  sake  of 
economy,  and  to  insure  a  dense  concrete  well  filling  the 
moulds  a  moderately  soft  mixture  is  recommended  for 
ordinary  purposes.  Where  the  pieces  to  be  moulded  are 
thin,  and  where  small  reinforcing  metal  rods  are  placed 
close  together  or  near  the  surface,  a  rather  wet  mixture 
may  be  necessary  to  insure  the  moulds  being  well  filled. 

Use  of  Quick-Setting  Cement. — In  the  manufacture 
of  such  articles  as  pipe,  fence  posts,  and  hollow  blocks, 
a  rather  large  proportion  of  quick-setting  cement  is 
sometimes  used,  the  object  being  to  reduce  the  weight 
and  consequent  freight  charges  by  means  of  a  strong 
mixture,  as  well  as  to  make  the  concrete  impervious  to 
Avater.  The  use  of  a  quick-setting  cement  permits  the 
moulds  to  be  removed  sooner  than  would  be  possible  with 
a  slow-setting  cement,  thus  reducing  the  number  of 
moulds  necessary  for  a  given  output.  Quick-setting  ce- 
ments are  not  recommended  for  such  purposes,  however, 
as  they  are  usually  inferior  to  those  which  set  slowly. 

Coloring  Cement  Work. — In  coloring  cement  work  the 
best  results  are  obtained  by  the  use  of  mineral  pig- 
ment.   The  coloring  matter,,  in  proportions  depending 


348  CEMENTS  AND  CONCRETES 


upon  the  desired  shade,  should  be  thoroughly  mixed  with 
the  dry  cement  before  making  the  mortar.  By  prepar- 
ing small  specimens  of  the  mortar  and  noting  the  color 
after  drying,  the  proper  proportions  may  be  determined. 

For  gray  or  black,  use  lampblack. 

For  yellow  or  buff,  use  yellow  ochre. 

For  brown,  use  umber. 

For  red,  use  Venetian  red. 

For  blue,  use  ultramarine. 

Depositing  Concrete. — Concrete  should  be  deposited 
in  layers  of  from  4  to  8  inches  and  thoroughly  tamped 
before  it  begins  to  harden.  The  tamping  required  will 
depetid  upon  the  consistency  of  the  mixture.  If  mixed 
very  dry  it  must  be  vigorously  rammed  to  produce  a 
dense  mass,  but  as  the  proportion  of  water  increases  less 
tamping  will  be  found  necessary.  Concrete  should  not 
be  dumped  in  place  from  a  height  of  more  than  4  feet, 
unless  it  is  again  mixed  at  the  bottom.  A  wooden  in- 
cline may  be  used  for  greater  heights.  Rammers  for 
ordinar;^  concrete  work  should  weigh  from  20  to  30 
pounds  and  have  a  face  not  exceeding  6  inches  square. 
A  smaller  face  than  this  is  often  desirable,  but  a  larger 
one  will  be  less  effective  in  consolidating  the  mass.  In 
cramped  situations  special  forms  must  be  employed  to 
suit  the  particular  conditions.  When  a  thickness  of 
more  than  one  layer  is  required,  as  in  foundation  work, 
two  or  more  layers  may  be  Avorked  at  the  same  time,  each 
layer  slightly  in  advance  of  the  one  next  above  it  and 
ail  being  allowed  to  set  together.  At  the  end  of  a  day 
there  is  usually  left  a  layer  partially  completed  which 
must  be  finished  the  next  day.  This  layer  should  not  be 
beveled  off,  but  the  last  batch  of  concrete  should  be 
tamped  behind  a  vertical  board  forming  a  step. 


HOW  TO  USE  THEM 


349 


To  avoid  introducing  a  plane  of  weakness  where  fresh 
concrete  is  deposited  upon  that  which  has  already  set, 
certain  precautions  have  to  be  observed.  The  surface  of 
the  old  work  should  be  clean  and  wet  before  fresh  ma- 
terial is  put  on,  a  thin  coat  of  neat  cement  grout  being 
sometimes  employed  to  insure  a  good  bond.  The  sur- 
face of  the  concrete  to  receive  an  additional  layer  must 
not  be  finished  off  smoothly,  but  should  offer  a  rough 
surface  to  bond  with  the  next  layer.  This  may  be  done 
by  roughing  the  surface  while  soft  with  pick  and  shovel, 
or  the  concrete  may  be  so  rammed  as  to  present  a  rough 
and  uneven  surface.  Wooden  blocks  or  scantling  are 
sometimes  embedded  several  inches  in  the  work  and  re- 
moved before  the  concrete  hardens,  thus  forming  holes 
or  grooves  to  be  filled  by  the  next  layer. 

Eetempering, — As  stated  before,  it  is  important  that 
concrete  be  tamped  in  place  before  it  begins  to  harden, 
and  for  this  reason  it  is  proper  to  mix  only  so  much  at  a 
time  as  is  required  for  immediate  use.  The  retempering 
of  concrete  which  has  begun  to  set  is  a  point  over  which 
there  is  much  controversy.  From  tests  made  in  this 
laboratory  it  would  appear  that  such  concrete  suffers  but 
little  loss  of  strength  if  thoroughly  mixed  with  sufficient 
water  to  restore  normal  consistence. 

The  time  required  for  concrete  to  set  depends  upon 
the  character  of  the  cement,  upon  the  amount  and  tem- 
perature of  the  water  used  in  mixing,  and  upon  the 
temperature  of  the  air.  Concrete  mixed  dry  sets  more 
quickly  than  if  mixed  wet,  and  the  time  required  for 
setting  decreases  as  the  temperature  of  the  water  rises„ 
Warm  air  also  hastens  the  setting. 

Concrete  Exposed  to  Sea-Water, — Portland  cement 
concrete  is  well  adapted  for  work  exposed  to  sea-water, 


350  CEMENTS  AND  CONCRETES 


but  when  used  for  -this  purpose  it  should  be  mixed  with 
fresh  water.  The  concrete  must  be  practically  imper- 
vious, at  least  on  the  surfaces,  and  to  accomplish  this 
purpose  the  materials  should  be  carefully  proportioned 
and  thoroughly  mixed.  It  is  also  of  great  importance 
that  the  concrete  be  well  compacted  by  tamping,  par- 
ticularly on  exposed  surfaces. 

Concrete'  Work  in  Freezing  Weather, — Although  it  is 
advisable  under  ordinary  conditions  to  discontinue  ce- 
ment work  in  freezing  weather,  Portland  cement  may  be 
used  without  serious  difficulty  by  taking  a  few  simple 
precautions.  As  little  water  as  possible  should  be  used 
in  mixing,  to  hasten  the  setting  of  the  concrete.  To 
prevent  freezing,  hot  water  is  frequently  used  in  mixing 
mortar  or  concrete,  and'with  the  same  object  in  view  salt 
is  added  in  amounts  depending  upon  the  degree  of  cold. 
A  common  practice  is  to  add  1  pound  of  salt  to  18  gal- 
lons of  water,  with  the  addition  of  1  oz.  of  salt  for  each 
degree  below  32°  F.  Either  of  the  above  methods  will 
give  good  results,  but  it  should  be  remembered  that  the 
addition  of  salt  often  produces  efflorescence.  It  seems 
to  be  a  fairly  well-established  fact  that  concrete  de- 
posited in  freezing  weather  will  ultimately  develop  full 
strength,  showing  no  injury  due  to  the  low  temperature. 

Rubble  Concrete. — In  massive  concrete  work  consider- 
able economy  may  often  be  introduced  by  the  use  of 
large  stones  in  the  body  of  the  work,  but  only  in  heavy 
foundations,  retaining  walls,  and  similar  structures 
should  this  form  of  construction  be  permitted.  In  plac- 
ing these  large  stones  in  the  work  the  greatest  care  must 
be  exercised  to  insure  each  being  well  bedded,  and  the 
concrete  must  be  thoroughly  tamped  around  them.  Each 


HOW  TO  USE  THEM 


351 


stone  should  be  at  least  4  inches  from  its  neighbor  and 
an  equal  distance  from  the  face  of  the  work. 

To  Face  Concrete. — A  coating  of  mortar  one-half 
inch  in  thickness  is  frequently  placed  next  the  form  to 
prevent  the  stone  or  gravel  from  showing  and  to  give 
a  smooth  and  impervious  surface.  If  in  preparing  this 
mortar  finely  crushed  stone  is  used  instead  of  sand,  th^^ 


•Sheet-metal  plate  used  in  facing  concrete* 
NO,  6. 


work  will  more  nearly  resemble  natural  stone.  A 
common  method  employed  in  facing  concrete  is  to  pro- 
vide a  piece  of  thin  sheet  metal  of  convenient  length 
and  about  8  to  10  inches  wide.  To  this  pieces  of  angle 
iron  are  riveted,  so  that  when  placed  next  to  the  mould 
a  narrow  space  is  formed  in  which  the  cement  mortar  is 
placed  after  the  concrete  has  been  deposited  behind  it. 
(No.  6.)    The  metal  plate  is  then  withdrawn  and  the 


352  CEMENTS  AND  CONCRETES 

concrete  well  tamped.  The  concrete  and  facing  mor- 
tar must  be  put  in  at  the  same  time  so  that  they  will 
set  together.  If  the  concrete  is  fairly  rich,  a  smooth 
surface  can  usually  be  produced  without  a  facing  of 
mortar  by  working  a  spade  up  and  down  between  the 
concrete  and  inner  face  of  the  mould,  thus  forcing  the 
larger  pieces  of  the  aggregate  back  from  the  surface. 

Wood  for  Forms. — Lumber  used  in  making  forms  for 
concrete  should  be  dressed  on  one  side  and  both  edges. 
The  expansion  and  distortion  of  the  wood  due  to  the 
absorption  of  water  from  the  concrete  frequently  make 
it  difficult  to  produce  an  even  surface  on  the  work,  and 
unless  the  forms  are  accurately  fitted  together  more  or 
less  water  will  find  its  way  out  through  the  cracks, 
carrying  some  of  the  cement  with  it.  A  method  some- 
times adopted  to  minimize  the  effect  of  expansion  is  to 
bevel  one  edge  of  each  board,  allowing  this  edge  to 
crush  against  the  square  edge  of  the  adjacent  board 
when  expansion  takes  place.  In  the  case  of  a  wooden 
core  or  inside  mold,  expansion  must  always  be  taken  intc 
consideration,  for  if  neglected  it  may  cause  cracks  or 
complete  rupture  of  the  concrete.  Sharp  edges  in  con* 
Crete  are  easily  chipped  and  should  be  avoided  by  plac- 
ing triangular  strips  to  the  corners  of  moulds.  To  pre- 
vent cement  from  sticking  to  the  forms  they  may  be 
given  a  coating  of  soft  soap  or  be  lined  with  paper. 
I'his  greatly  facilitates  their  removal  and  enables  them 
to  be  used  again  with  but  little  scraping.  A  wire  brush 
answers  best  for  cleaning  the  forms. 

Concrete  Sidewalks. — A  useful  and  comparatively 
simple  application  of  concrete  is  in  the  construction  of 
sidewalks,  for  which  purpose  it  has  been  used  with 
marked  success  for  a  number  of  years. 


HOW  TO  USE  THEM 


353 


Excavation  and  Preparation  of  Subgrade. — The 
ground  is  excavated  to  subgrade  and  well  consolidated 
by  ramming  to  prepare  it  for  the  subfoundation  of 
stone,  gravel  or  cinders.  The  depth  of  excavation  will 
depend  upon  the  climate  and  nature  of  the  ground, 
being  deeper  in  localities  where  heavy  frosts  occur  or 
where  the  ground  is  soft  than  in  climates  where  there 
are  no  frosts.  In  the  former  case  the  excavation  should 
be  carried  to  a  depth  of  12  inches,  whereas  in  the  latter 
from  4  to  6  inches  will  be  sufficient.  No  roots  of  trees 
should  be  left  above  the  subgrade. 

The  Subfoundation. — The  foundation  consists  of  a 
layer  of  loose  material,  such  as  broken  stone,  gravel, 
or  cinders,  spread  over  the  subgrade  and  well  tamped  to 
secure  a  firm  base  for  the  main  foundation  of  concrete 
which  is  placed  on  top.  It  is  most  important  that  the 
subfoundation  be  well  drained  to  prevent  the  accumula- 
tion of  water,  which,  upon  freezing,  would  lift  and  crack 
the  walk.  For  this  purpose  it  is  well  to  provide  drain 
tile  at  suitable  points  to  carry  off  any  water  which  may 
collect  under  the  concrete.  An  average  thickness  for. 
subfoundation  is  4  to  6  inches,  although  in  warm  cli- 
mates, if  the  ground  is  firm  and  wells  drained,  the  sub- 
foundation  may  only  be  2  to  3  inches  thick  or  omitted 
altogether. 

The  Foundation, — The  foundation  consists  of  a  layer 
of  concrete  deposited  on  the  subfoundation  and  carry- 
ing a  surface  layer  or  wearing  coat  of  cement  mortar.  If 
the  ground  is  firm  and  the  subfoundation  well  rammed 
in  place  and  properly  drained,  great  strength  will  not  be 
required  of  the  concrete,  which  may,  in  such  cases,  be 
mixed  in  about  the  proportions  1-3-6,  and  a  depth  of  only 
3  to  4  inches  will  be  required.    Portland  cement  should 


354  CEMENTS  AND  CONCEETES 


be  used  and  stone  or  gravel  under  1  inch  in  size,  the  con- 
crete being  mixed  of  medium  consistency,  so  that 
moisture  will  show  on  the  surface  without  excessive 
tamping. 

The  Top  Dressing  or  Wearing  Surface. — To  give  a 
neat  appearance  to  the  finished  walk,  a  top  dressing  of 
cement  mortar  is  spread  over  the  concrete,  well  worked 
in,  and  ^brought  to  a  perfectly  smooth  surface  with 
straightedge  and  float.  This  mortar  should  be  mixed 
in  the  proportion  1  part  cement  to  2  parts  sand,  sharp 
coarse  sand  or  screenings  below  one-fourth  inch  of  some 
hard,  tough  rock  being  used.  The  practice  of  making 
the  concrete  of  natural  cement  and,  the  wearing  surface 
of  Portland  is  not  to  be  commended,  owing  to  a  tendency 
for  the  two  to  separate. 

Details  of  Construction. — A  cord  stretched  between 
stakes  w^ll  serve  as  a  guide  in  excavating,  after  which 
the  bottom  of  the  trench  is  well  consolidated  by  ram- 
ming; any  loose  material  below  subgrade  is  then  spread 
over  the  bottom  of  the  trench  to  the  desired  thickness 
and  thoroughly  compacted.  Next,  stakes  are  driven 
along  the  sides  of  the  walk;  spaced  4  to  6  feet  apart, 
and  their  tops  made  even  with  the  finished  surface  of 
the  walk,  which  should  have  a  transverse  slope 
of  one-fourth  inch  to  the  foot  for  drainage.  Wooden 
strips  at  least  inches  thick  and  of  a  suitable  depth 
are  nailed  to  these  stakes  to  serve  as  a  mould  to  concrete. 
By  carefully  adjusting  these  strips  to  the  exact  height  of 
the  stakes  they  may  be  used  as  guides  for  the  straight- 
edge in  levelling  off  the  concrete  and  wearing  surface. 
The  subfoundation  is  well  sprinkled  to  receive  the  con- 
crete, which  is  deposited  in  the  usual  manner,  well 
tamped  behind  a  board  set  vertically  across  the  trench, 


HOW  TO  USE  THEM 


355 


and  levelled  off  with  a  straightedge  as  shown  in  Fig.  7, 
leaving  one-half  to  1  inch  for  the  wearing  surface. 
Three-eighths  inch  sand  joints  are  provided  at  intervals 
of  6  to  8  feet  to  prevent  expansion  cracks,  or,  in  case  of 
settlement,  to  confine  the  cracks  to  these  joints.  This  is 
dene  either  by  depositing  the  concrete  in  sections,  or  by 
dividing  it  into  such  sections  with  a  spade  when  soft  and 
filling  the  joints  with  sand.  The  location  of  each  joint 
is  marked  on  a  w^ooden  frame  for  future  reference. 


NO.  7. 


Care  must  be  exercised  to  prevent  sand  or  any  other 
material  from  being  dropped  on  the  concrete,  and  thus 
preventing  a  proper  union  with  the  wearing  surface.  No 
section  should  be  left  partially  completed  to  be  finished 
with  the  next  batch  or  left  until  the  next  day.  Any  con- 
crete left  after  the  completion  of  a  section  should  be 
mixed  w^ith  the  next  batch. 

It  is  of  the  utmost  importance  to  follow  up  closely  the 
concrete  work  with  the  top  dressing  in  order  that  the 


S56  CEMENTS  AND  CONCEETES 


two  may  set  together.  This  top  dressing  should  be 
worked  well  over  the  concrete  with  a  trowel,  and  levelled 
with  a  straightedge  (No.  7)  to  secure  an  even  surface. 
Upon  the  thoroughness  of  this  operation  often  depends 
the  success  or  failure  of  the  walk,  since  a  good  bond  be- 
tween the  wearing  surface  and  concrete  base  is  absolute- 
ly essential.  The  mortar  should  be  mixed  rather  stiff. 
As  soon  as  the  film  of  water  begins  to  leave  the  surface, 
a  wooden  float  is  used,  followed  up  by  a  plasterer's 
trowel,  the  operation  being  similar  to  that  of  plastering 
a  wall.  The  floating,  though  necessary  to  give  a  smooth 
surface,  will,  if  continued  too  long,  bring  a  thin  layer  of 
neat  cement  to  the  surface  and  probably  cause  the  walk 
to  crack. 


Jointer  used  in  dividing  walk 
into  sections. 

NO.  8. 


The  surface  is  now  divided  into  sections  by  cutting  en-  . 
tirely  through,  exactly  over  the  joints  in  the  concrete. 
This  is  done  with  a  trowel  guided  by  a  straightedge, 
after  which  the  edges  are  rounded  oft*  with  a  special  tool 
called  a  jointer,  having  a  thin  shallow  tongue  (No.  8). 
These  sections  may  be  subdivided  in  any  manner  desired 
for  the  sake  of  appearance. 

A  special  tool  called  an  edger  (No.  9)  is  run  round  the 
outside  of  the  walk  next  to  the  mould,  giving  it  a  neat 
rounded  edge.    A  toothed  roller  (No.  10)  having  small 


HOW  TO  USE  THEM  357 

projections  on  its  face  is  frequently  used  to  produce 
slight  indentations  on  the  surface,  adding  somewhat  to 


Tool  used  in  rounding  edges. 
NO.  9. 

the  appearance  of  the  walk.  The  completed  work  must 
be  protected  from  the  sun  and  kept  moist  by  sprinkling 


'Roller  used  in  finishing  surface 
NO.  10. 


for  several  days.  In  freezing  weather  the  same  precau- 
tions should  be  taken  as  in  other  classes  of  concrete 
work. 


358  CEMENTS  AND  CONCEETES 


Concrete  Basement  Floors, — Basement  floors  in  dwell- 
ing houses  as  a  rule  require  only  a  moderate  degree  of 
strength,  although  in  cases  of  very  wet  basements,  where 
water  pressure  from  beneath  has  to  be  resisted,  greater 
strength  is  required  than  would  otherwise  be  necessary. 
The  subfoundation  should  be  well  drained,  sometimes  re- 
quiring the  use  of  tile  for  carrying  off  the  water.  The 
rules  given  for  constructing  concrete  sidewalks  apply 
equally  well  to  basement  floors.  The  thickness  of  the 
concrete  foundation  is  usually  from  3  to  5  inches,  ac- 
cording to  the  strength  desired,  and  for  average  work  a 
1-3-6  mixture  is  sufficiently  rich.  Expansion  joints  are 
frequently  omitted,  since  the  temperature  variation  is 
less  than  in  outside  work,  but  since  this  omission  fre- 
quently gives  rise  to  unsightly  cracks,  their  use  is  recom- 
mended in  all  cases.  It  will  usually  be  sufficient  to 
divide  a  room  of  moderate  size  into  four  equal  sections, 
separated  by  %  inch  sand  joints.  The  floor  should  be 
given  a  slight  slope  toward  the  center  or  one  corner,  with 
provision  at  the  lowest  point  for  carrying  off  any  water 
that  may  accumulate. 

Concrete  Stable  Floors  and  Driveivays, — Concrete 
stable  floors  and  driveways  are  constructed  in  the  same 
general  way  as  basement  floors  and  sidewalks,  but  with 
a  thicker  foundation,  on  account  of  the  greater  strength 
required.  The  foundation  may  well  be  6  inches  thick, 
.with  a  10  inch  wearing  surface.  An  objection  often 
sometimes  raised  against  concrete  driveways  is  that  they 
become  slippery  when  wet;  but  this  fault  is  in  a  great 
measure  overcome  by  dividing  the  wearing  surface  into 
small  squares  about  4  inches  on  the  side,  by  means  of  tri- 
angular grooves  %  of  an  inch  deep.   This  gives  a  very 


HOW  TO  USE  THEM 


359 


neat  appearance  and  furnishes  a  good  foothold  for 
horses. 

Concrete  Steps. — Concrete  may  be  advantageously 
used  in  the  construction  of  steps,  particularly  in  damp 
places,  such  as  areaways  and  cellars  of  houses,  and  in 
the  open,  where  the  ground  is  terraced,  concrete  steps 
and  walks  can  be  made  exceedingly  attractive.  Where 
the  ground  is  firm  it  may  be  cut  away  as  nearly  as  pos- 
sible in  the  form  of  steps,  with  each  step  left  two  or 
three  inches  below  its  finished  level.  The  steps  are 
formed,  beginning  at  the  top,  by  depositing  the  con- 


Keinforced  concrete  steps. 

NO.  11. 


Crete  behind  vertical  boards  so  placed  as  to  give  the  nec- 
essary thickness  to  the  risers  and  projecting  high  enough 
to  serve  as  a  guide  in  leveling  off  the  tread.  Such  steps 
may  be  reinforced  where  greater  strength  is  desired  or 
where  there  is  danger  of  cracking,  due  to  the  settlement 
of  the  ground. 

Where  the  nature  of  the  ground  will  not  admit  of  its 
being  cut  away  in  the  form  of  steps,  the  risers  are 


360  CEMENTS  AND  CONCRETES 


molded  between  two  vertical  forms.  The  front  one  may 
be  a  smooth  board,  but  the  other  should  be  a  piece  of 
thin  sheet  metal,  which  is  more  easily  removed  after  the 
earth  has  been  tamped  in  behind  i-t.  A  simple  method 
of  reinforcing  steps  is  to  place  a  %  inch  steel  rod  in  each 
corner,  and  thread  these  with  i/4  inch  rods  bent  to  the 
shape  of  the  steps,  as  shown  in  No.  11,  the  latter  being 
placed  about  2  feet  apart.  For  this  class  of  work  a  rich 
Portland  cement  concrete  is  recommended,  with  the  use 
of  stone  or  gravel  under  %  inch  in  size.  Steps  may  be 
given  a  ^  inch  wearing  surface  of  cement  mortar  mixed 
in  the  proportion  of  1  part  cement  to  2  parts  sand.  This 
system,  as  well  as  many  others,  is  well  adapted  for  stair- 
ways in  houses. 

Reinforced  Concrete  Fence  Posts. — Comparison  of  dif- 
ferent Post  Materials:  There  is  a  constantly  increasing 
demand  for  some  form  of  fence  posts  which  is  not  sub- 
ject to  decay.  The  life  of  wooden  posts  is  very  limited, 
and  the  scarcity  of  suitable  timber  in  many  localities 
has  made  it  imperative  to  find  a  substitute.  A  fence 
post,  to  prove  thoroughly  satisfactory,'  must  fulfil  three 
conditions:  (1)  It  must  be  obtainable  cost;  (2)  it  must 
possess  sufficient  strength  to  meet  the  demands  of  gen- 
eral farm  use;  (3)  it  must  not  be  subject  to  decay,  and 
must  be  able  to  withstand  successfully  the  effects  of 
water,  frost  and  fire.  Although  iron  posts  of  various 
designs  are  frequently  used  for  ornamental  purposes, 
their  adoption  for  general  farm  use  is  prohibited  by  their 
excessive  cost.  Then,  too,  iron  posts  exposed  to  the 
weather  are  subject  to  corrosion,  to  prevent  which  neces- 
sitates repainting  from  time  to  time,  and  this  item  will 
entail  considerable  expense  in  cases  where  a  large  nura- 
ber  of  posts  are  to  be  used, 


HOW  TO  USE  THEM  361 


At  the  present  time  the  material  which  seems  most 
nearly  to  meet  these  requirements  is  i^einforeed  con- 
crete. The  idea  of  constructing  fence  posts  of  concrete 
reinforced  with  iron  or  steel  is  by  no  means  a  new  one, 
but,  on  the  contrary,  such  posts  have  been  experimented 
with  for  years,  and  a  great  number  of  patents  have  been 
issued  covering  many  of  the  possible  forms  of  reinforce- 
ment. It  is  frequently  stated  that  a  reinforced  con- 
crete post  can  be  made  and  put  in  the  ground  for  the 
same  price  as  a  wooden  post.  Of  course  this  will  de- 
pend in  any  locality  upon  the  relative  value  of  wood  and 
the  various  materials  which  go  to  make  up  the  concrete 
post,  but  in  the  great  majority  of  cases  wood  will  prove 
the  cheaper  material  in  regard  to  first  cost.  On  the 
other  hand,  a  concrete  post  will  last  indefinitely,  its 
strength  increasing  with  age,  whereas  the  wooden  post 
must  be  replaced  at  short  intervals,  probably  making  it 
more  expensive  in  the  long  run. 

In  regard  to  strength,  it  must  be  borne  in  mind  that 
it  is  not  practicable  to  make  concrete  fence  posts  as 
strong  as  wooden  posts  of  the  same  size  j  but  since  wooden 
posts,  as  a  rule,  are  many  times  stronger  than  is  neces- 
sary, this  difference  in  strength  should  not  condemn  the 
use  of  reinforced  concrete  for  this  purpose.  Moreover, 
strength  in  many  cases  is  of  little  importance,  the  fence 
being  used  only  as  a  dividing  line,  and  in  such  cases 
small  concrete  posts  provide  ample  strength  and  present 
a  very  uniform  and  neat  appearance.  In  any  case,  to 
enable  concrete  posts  to  withstand  the  loads  they  are 
called  upon  to  carry,  sufficient  strength  may  be  secured 
by  means  of  reinforcement,  and  where  great  strength  is 
required  this  may  be  obtained  by  using  a  larger  post 
with  a  greater  proportion  of  metal  and  well  braced,  as 


362  CEMENTS  AND  CONCRETES 


is  usual  in  such  cases.  In  point  of  durability,  concrete 
is  unsurpassed  by  any  material  of  construction.  It  offers 
a  perfect  protection  to  the  metal  reinforcement  and  is 
not  itself  affected  by  exposure,  so  that  a  post  constructed 
of  concrete  reinforced  with  steel  will  last  indefinitely  and 
require  no  attention  in  the  way  of  repairs. 

Reinforcement. — No  form  of  wooden  reinforcement, 
either  on  the  surface  or  within  the  post,  can  be  recom- 
mended. If  on  the  surface^  the  wood  will  soon  decay, 
and  if  a  wooden  core  is  used  it  will^  in  all  probability, 
swell  by  the  absorption  of  moisture  and  crack  the  post. 
The  use  of  galvanized  wire  is  sometimes  advocated,  but 
if  the  post  is  properly  constructed  and  a  good  concrete 
used,  this  precaution  against  rust  will  be  unnecessary, 
since  it  has  been  fully  demonstrated  by  repeated  tests 
that  concrete  protects  steel  perfectly  from  rust.  If 
plain,  smooth  wire  or  rods  are  used  for  reinforcement 
they  should  be  bent  over  at  the  ends  or  looped  to  pre- 
vent slipping  in  the  concrete.  Twisted  fence  wire  may 
usually  be  obtained  at  a  reasonable  cost  and  is  very  well 
suited  for  this  purpose.  Barbed  wire  has  been  proposed 
and  is  sometimes  used,  although  the  barbs  make  it  ex- 
tremely difficult  to  handle.  For  the  sake  of  economy  the 
smallest  amount  of  metal  consistent  with  the  desired 
strength  must  be  used,  and  this  requirement  makes  it 
necessary  to  place  the  reinforcement  near  the  surface, 
where  its  strength  is  utilized  to  greatest  advantage,  with 
only  enough  concrete  on  the  outside  to  form  a  protective 
covering.  A  reinforcing  member  in  each  corner  of  the 
post  is  probably  the  most  efficient  arrangement. 

Concrete  for  Fence  Posts. — The  concrete  should  be 
mixed  with  Portland  cement  in  about  the  proportions 
1-2^-5,  broken  stone  or  gravel  under  %  inch  being  used. 


HOW  TO  USE  THEM  363 

In  cases  where  the  aggregate  contains  pieces  smaller 
than  14  inch,  less  sand  may  be  used,  and  in  some  cases 
it  may  be  omitted  altogether.  A  mixture  of  medium  con- 
sistency is  recommended  on  the  ground  that  it  fills  the 
molds,  better  and  with  less  tamping  than  if  mixed  quite 
dry. 

Molds  for  Fence  Posts. — Economy  points  to  the  use 
of  a  tapering  post,  which,  fortunately,  offers  no  diffi- 
culties in  the  way  of  molding.    All  things  considered, 


Wooden  jnoldLfor  making  fence  posts  with  four  tapering  sides. 
NO.  12. 


wooden  molds  will  be  found  most  suitable.  They  can 
easily  and  quickly  be  made  in  any  desired  form  and  size. 
Posts  may  be  molded  either  in  a  vertical  or  horizontal 
position,  the  latter  being  the  simpler  and  better  method. 
If  molded  vertically  a  wet  mixture  is  necessary,  requir- 
ing a  longer  time  to  set,  with  the  consequent  delay  in 
removing  the  molds.  No.  12  shows  a  simple  mold,  which 
has  been  used  with  satisfactory  results  in  this  laboratory. 


364  CEMENTS  AND  CONCRETES 


This  mold  has  a  capacity  of  four  posts,  but  larger  molds 
could  easily  be  made  on  the  same  principle.  It  consists 
of  two  end  pieces,  (a)  carrying  lugs,  (b)  between  which 
are  inserted  strips  (c).  The  several  parts  are  held  to- 
gether with  hooks  and  eyes,  as  shown  in  No.  12.  To  pre- 
vent any  bulging  of  the  side  strips  they  are  braced,  as 
illustrated.  Dressed  lumber  at  least  1  inch  thick,  and 
preferably  1%  inches,  should  be  used.    In  No.  12  the 


.-Wooden  mold  for  making  fence  posts  with  two  tapering  sides. 
NO.  13. 


post  measures  6  by  6  inches  at  the  bottom,  6  by  3  at  the 
top,  and  7  feet  in  length,  having  two  parallel  sides.  If 
it  is  desired  to  have  the  posts  square  at  both  ends  the 
mold  must  be  arranged  as  in  No.  13.  This  latter  form 
of  post  is  not  as  strong  as  the  former,  but  requires  less 
concrete  in  its  construction.  Great  care  in  tamping  is 
necessary  to  insure  the  corners  of  the  mold  being  well 


HOW  TO  USE  THEM 


365 


filled,  and  if  this  detail  is  not  carefully  watched,  the 
metal,  being  exposed  in  places,  will  be  subject  to  rust. 

Attaching  Fence  Wires  to  Posts. — Various  devices  have 
been  suggested  for  attaching  fence  wires  to  the  posts,  the 
object  of  each  being  to  secure  a  simple  and  permanent 
fastener  or  one  admitting  of  easy  renewal  at  any  time. 
Probably  nothing  will  answer  the  purpose  better  than  a 
long  staple  or  bent  wire  well  embedded  in  the  concrete, 
being  twisted  or  bent  at  the  end  to  prevent  extraction. 
Galvanized  metal  must  be  used  for  fasteners,  since  they 


are  not  protected  by  the  concrete.  A  piece  of  small  flex- 
ible wire,  about  two  inches  in  length,  threading  the  staplf 
and  twisted  several  times  with  a  pair  of  pliers,  holds  the 
line  wire  in  position.    (No.  14.) 

Molding  and  Curing  Posts. — For  the  proper  method  of 
mixing  concrete  see  previous  pages.  It  is  recommended 
that  only  so  much  concrete  be  mixed  at  one  time  as  can 
be  used  before  it  begins  to  harden ;  but  if  an  unavoidable 
delay  prevents  the  posts  being  molded  until  after  the 


•Detail  showing  method  ot 
taching  wire  to  post. 

NO.  14. 


366  CEMENTS  AND  CONCRETES 


concrete  has  begun  to  set,  it  is  thought  that  a  thorough 
regauging  with  sufficient  water  to  restore  normal  con- 
sistency will  prevent  any  appreciable  loss  of  strength, 
though  the  concrete  may  have  been  standing  one  or  two 
hours.  In  using  a  mold  similar  to  those  illustrated  in 
Nos.  12  and  13  it  is  necessary  to  provide  a  perfectly 
smooth  and  even  platform  of  a  size  depending  upon  the 
number  of  posts  to  be  molded.  A  cement  floor  if  accessi- 
ble may  be  used  to  advantage.  The  molds  when  in  place 
are  given  a  thin  coating  of  soft  soap,  the  platform  or 
cement  floor,  serving  as  bottom  of  mold,  being  treated  in 
the  same  way.  About  1%  inches  is  spread  evenly  over 
the  bottom  and  carefully  tamped,  so  as  to  reduce  it  to  a 
thickness  of  about  1  inch.  A  piece  of  board  cut  as  in 
No.  12  will  be  found  useful  in  leveling  off  the  concrete  to 
the  desired  thickness  before  tamping.  On  top  of  this 
layer  two  reinforcing  members  are  placed  about  1  inch 
from  the  sides  of  the  mold.  The  molds  are  then  filled 
and  tamped  in  thin  layers  to  the  level  of  the  other  two 
reinforcing  members,  the  fasteners  for  fence  wires  being 
inserted  during  the  operation.  These  reinforcing  mem- 
bers are  adjusted  as  were  the  first  two,  and  the  remain- 
ing 1  inch  of  concrete  tamped  and  leveled  off,  thus  com- 
pleting the  post  so  far  as  molding  is  concerned.  To  avoid 
sharp  edges,  which  are  easily  chipped,  triangular  strips 
may  be  placed  in  the  bottom  of  mold  along  the  sides,  and 
when  the  molds  have  been  filled  and  tamped,  similar 
strips  may  be  inserted  on  top.  The  top  edges  may  be 
beveled  with  a  trowel  or  by  running  an  edging  tool  hav- 
ing a  triangular  projection  on  its  bottom  along  the  edges. 
Such  a  tool  is  shown  in  No.  15,  and  can  easily  be  made 
of  wood  or  metal.  It  is  not  necessary  to  carry  the  bevel 
below  the  ground  line. 


HOW  TO  USE  THEM 


867 


The  ends  and  sides  of  the  mold  may  be  removed  after 
twenty-four  hours,  but  the  posts  should  not  be  handled 
for  at  least  one  week,  during  which  time  they  must  be 
well  sprinkled  several  times  daily  and  protected  from  sun 
and  wind.  The  intermediate  strips  may  be  carefully 
withdrawn  at  the  end  of  two  or  three  days,  but  it  is  bet-  - 
ter  to  leave  them  in  place  until  the  posts  are  removed. 
Although  a  post  may  be  hard  and  apparently  strong 
when  one  week  old^  it  will  not  attain  its  full  strength  in 
that  length  of  time,  and  must  be  handled  with  the  utmost 
care  to  prevent  injury.  Carelessness  in  handling  green 
posts  frequently  results  in  the  formation  of  fine  cracks, 
which  though  unnoticed  at  the  time,  give  evidence  of 
their  presence  later  in  the  failure  of  the  posts. 


Tool  used  for  beveling  edges  of 
posts. 

NO.  15. 


Posts  ishould  be  allowed  to  cure  for  at  least  sixty  days 
before  being  placed  in  the  ground,  and  for  this  purpose 
it  is  recommended  that  when  moved  from  the  molding 
platform  they  be  placed  upon  a  smooth  bed  of  moist  sand 
and  protected  from  the  sun  until  thoroughly  cured.  Dur- 
ing this  period  they  should  receive  a  thorough  drench- 
ing  at  least  once  a  day. 


368 


CEMENTS  AND  CONCEETES 


The  lif 3  of  the  molds  will  depend  upon  the  care  with 
which  they  are  handled.  A  coating  of  mineral  oil  or 
shellac  may  be  used  instead  of  soap  to  prevent  the  cement 
from  sticking  to  the  forms.  As  soon  as  the  molds  are 
\removed  they  should  be  cleaned  with  a  wire  brush  before 
[being  used  again. 

The  cost  of  reinforced  concrete  fence  posts  depends 
in  each  case  upon  the  cost  of  labor  and  materials,  and 
must  necessarily  vary  in  different  localities.  An  esti- 
mate in  any  particular  case  can  be  made  as  follows:  One 
cubic  yard  of  concrete  will  make  twenty  posts  measuring 
6  inches  by  6  inches  at  the  bottom,  6  inches  by  3  inches 
at  the  top,  and  7  feet  long,  and  if  mixed  in  the  propor- 


tions 1-2^-5,  requires  approximately : 

1.16  barrels  of  cement,  at  $2   $2.32 

0.44  cubic  yard  of  sand,  at  75  cts  33 

0.88  cubic  yard  of  gravel,  at  75  cts  66 


Materials  for  1  cubic  yard  cement  $3.21 

Concrete  for  one  post  17 

28  feet  of  0.16  inch  steel  wire,  at  3  cts  a  pound  06 

Total  cost  of  concrete  and  metal  for  1  post  23 


To  this  must  be  added  the  cost  of  mixing  concrete, 
molding  and  handling  posts,  and  the  costs  of  molds,  an 
addition  which  should  not  in  any  case  exceed  7  cents, 
making  a  total  of  30  cents  per  post. 

Concrete  Building  Blocks. — Concrete  building  blocks, 
or  cement  blocks,  as  they  are  frequently  called,  are  more 
extensively  used  now  than  ever  before.  These  blocks 
are  molded  hollow  primarily  to  reduce  their  cost,  but 
ihis  hollow  construction  serves  other  useful  purposes  at 
the  same  time.    The  fundamental  principles  governing 


HOW  TO  USE  THEM 


369 


ordinary  concrete  work,  so  far  as  proportioning  and 
mixing  materials  is  concerned,  apply  equally  well  to  the 
manufacture  of  building  blocks,  and  it  should  be  borne 
in  mind  that  strength  and  durability  can  not  be  obtained 
by  the  use  of  any  machine  unless  the  cement,  sand,  and 
aggregate  are  of  good  quality,  properly  proportioned 
and  well  mixed.  The  aggregate  for  blocks  of  ordinary 
size  should  be  crushed  stone  or  gravel  not  larger  than 
l^  inch.  One  of  the  chief  causes  of  complaint  against 
the  concrete  building  block  is  its  porosity,  but  this  defect 
is  in  a  great  measure  due  to  the  fact  that  in  an  endeavor 
to  economize  too  little  cement  is  frequently  used.  It  is 
not  unusual  to  give  the  blocks  a  facing  of  cement  mor- 
tar consisting  of  about  2  parts  sand  to  1  of  cement,  while 
the  body  of  the  block  is  composed  of  a  concrete  of  suffi- 
cient strength,  though  not  impervious.  This  outside 
layer  of  mortar  adds  practically  nothing  to  the  strength 
of  the  block,  and  is  used  simply  to  give  a  uniform  sur- 
face and  to  render  the  face  of  the  wall  more  clearly  im- 
pervious to  water. 

It  would  not  be  practicable  as  a  rule  to  attempt  the 
manufacture  of  concrete  blocks  without  one  of  the  many 
forms  of  molding  machines  designed  for  the  purpose,  noi 
would  it  be  economical  to  purchase  such  a  machine  un- 
less a  sufficient  number  of  blocks  were  required  to  ju;stify 
such  an  outlay.  Blocks  in  almost  any  desired  shape  and 
size,  with  either  plain  or  ornamental  faces,  may  be  ob- 
tained on  the  market^  and  in  the  great  majority  of  cases 
it  is  best  to  buy  them  from  some  reliable  firm.  Among 
the  advantages  claimed  for  hollow  concrete  block  con- 
struction may  be  mentioned  the  following : 

(1)  Hollow  block  conistruction  introduces  a  saving  of 
material  over  brick  or  stone  masonry. 


370  CEMENTS  AND  CONCRETES 


(2)  The  cost  of  laying  concrete  blocks  is  less  than  for 
brick  work.  This  is  due  to  the  fact  that  the  blocks,  being 
larger/  require  a  much  smaller  number  of  joints  and 
less  mortar,  and,  being  hollow,  are  of  less  weight  than 
solid  brick  work. 

(3)  A  wall  constructed  of  good  concrete  blocks  is  as 
strong  or  stronger  than  a  brick  wall  of  equal  thickness. 

(4)  Concrete  blocks,  being  easily  molded  to  any  de- 
sired form,  will  prove  to  be  a  far  more  economical  build- 
ing material  than  stone,  which  has  to  be  dressed  to 
shape. 

(5)  Experience  has  proved  concrete  to  be  a  most  cx- 
<iellent  fire  resisting  material. 

(6)  Concrete  blocks,  being  hollow,  tend  to  prevent 
sudden  changes  of  temperature  within  a  house,  making 
it  cool  in  summer  and  easily  heated  in  winter. 

(7)  The  hollow  spaces  provide  an  easy- means  for 
running  pipes  and  electric  wires.  These  spaces  may  also 
be  used  wholly  or  in  part  for  heating  and  ventilating 
flues. 

Tests  of  Concrete  Fence  Posts. — In  the  summer  of 
1904  a  number  of  reinforced  concrete  fence  posts  were 
made  for  experimental  purposes,  with  a  view  to  deter- 
mining their  adaptability  for  general  use.  These  posts 
were  made  both  with  and  without  reinforcement^  and 
tested  at  the  age  of  90  days.  The  reinforcement,  rang- 
ing from  0.27  per  cent,  to  1.13  per  cent.,  consisted  of 
four  round  steel  rods,  one  in  each  corner  of  post  about 
1  inch  from  surface,  the  posts  having  a  uniform  cross- 
section  of  6  by  6  inches.  The  posts  were  molded  in  a 
horizontal  position,  as  this  was  found  by  trial  to  be  more 
satisfactory  than  molding  them  vertically. 


HOW  TO  USE  THEM 


371 


The  concrete  was  mixed  moderately  soft,  crushed  stone 
between  1  inch  and  l^  inch  and  gravel  under  %  inch 
being  used  as  aggregate.  River  sand,  fairly  clean  and 
sharp,  was  employed  with  Portland  cement.  The  posts 
were  tested  as  beams,  supported  at  both  ends  and  loaded 
at  the  centre,  with  spans  varying  from  4  feet  to  5  feet  6 
inches.  An  attempt  was  made  to  prevent  slipping  by 
providing  the  reinforcing  rods  with  collars  and  set 
screws  at  the  ends,  but  in  every  case,  with  but  two  ex- 
ceptions, the  rods  slipped  under  a  comparatively  light 
load,  thus  showing  the  necessity  for  some  form  of  me- 
chanical bond.  As  would  be  expected,  those  posts  which 
were  not  reinforced  possessed  very  little  strength. 


A  series  of  tests  was  made  with  sheet-iron  reinforce- 
ment, in  the  form  of  round  and  square  pipes,  embedded 
in  the  posts,  but  these  posts,  though  developing  consid- 
erable strength,  proved  less  economical  than  those  rein- 
forced with  plain  rods^  and  at  the  same  time  were  less 
simple  in  construction.  The  results  of  these  tests,  as  re- 
corded in  Table  I.,  do  not  properly  represent  the  strength 
of  similar  posts  in  which  some  form  of  mechanical  bond 
is  provided  to  develop  the  full  strength  of  the  reinforce- 
ment. 


Method   of  testing 
posts  under  static  loads. 


372  CEMENTS  AND  CONCEETES 


Equivalent 
Maximum 
Load  on 
4-foot 

1  h^^^m^^^nn^M^^^^ 

Equivalent 
Load  on 

4-foot  Can- 
tilever at 

1  « 

Maximum 
Load. 

Load 
at  First 
Crack. 

1 

mBmBmmmmmm 

Per  Cent 
Rein'force- 

I        :  :  :  :  :  ifiRSSRSSSSSSgggggggggSSSS 

I 

6 

HOW  TO  USE  THEM  373 


Equivalent 
Maximum 
Load  on 
4-foot 

I                                    III  m  iSi 

Equivalent 
Load  on 

4-foot  Can- 
tilever at 

^  fi^sliSiiiiiiiiiiigii  II :  iie  iil 

Maximum 
Load. 

Poimds. 
3,545 
4,200 
3,575 
5, 150 
4,300 
4,240 
2,600 
3,160 
3,345 
3,840 
2,600 
3,820 
5,080 
3,100 
4,900 
4,460 
2,900 
2,320 
3,270 
4,300 

4,000 
4,000 
4,660 

6,320 
5,880 
6,040 

2,450 
2,660 
2,400 

Load 
at  First 
Crack. 

11 i  III  ill 

i 

|°o|oo|oooo|00oo^ooo    ooo    ooo  goo 

xture. 

i0^iOut>iOiOut)iO^»OiOiCiOiCiO>0>OiOut)iC      'O^kO      iCiO»0  "tiiOiO 

(N  <^^  (^^  w  CO  CO  c<i  c<i  c<i     c<i                                 <n  c<J        c<i  C4  (N  c^chch 

Per  Cent 
of 

Reinforce- 
ment. 

^^M^^^^:^^^^.^^^^^^^^^  222 

Kind  of  Reinforcement. 

Plain  Steel  Rods  

 do  

 do  

 do  

 do  

 do  

 do  

 do  

 do  

 do  

 do  

do 

 do  

 do  

 do  

 do  

 do  

 do  

 do  

Pipe  5  inches  diameter,  1-40 

inch  thick  

 do  

 do  

□  5  by  5  inches,  1-40  inch 

thick  

 do  

 do  

X  5  by  5  inches,  1-40  inch 

thick  

 do  

 do  

374  CEMENTS  AND  CONCRETES 


In  order  to  obtain  more  data  on  the  subject,  this  in- 
vestigation has  been  supplemented  by  a  second  series  of 
tests,  the  results  of  which  form  the  subject  matter  for 
the  sections  on  concrete  fence  posts  and  are  expressed 
numerically  in  Table  II. 

In  these  tests  it  was  decided  to  make  the  posts  taper- 
ing in  order  to  economize  material  and  reduce  their 
weight.  For  the  concrete,  Portland  cement,  river  sand, 
and  gravel  were  used  in  the  proportion  1-21/2-5,  meas- 
ured by  volume,  the  gravel  being  screened  below  I/2  inch. 
Sufficient  water  was  used  in  mixing  to  produce  a  plastic 
mass^  requiring  only  a  moderate  degree  of  tamping  to 
bring  water  to  the  surface.  The  posts  were  molded  and 
kept  under  wet  burlap  for  four  weeks,  and  tested  at  the 
end  of  sixty  days.  The  reinforcing  members  were  placed 
in  the  corners  of  the  posts  about  1  inch  from  the  surface, 
being  looped  and  bent,  as  indicated  in  Table  II.  These 
posts  were  not  designed  with  a  view  to  developing  the 
ultimate  compressive  strength  of  the  concrete,  but  where 
greater  strength  is  necessary  it  may  be  obtained  at  small 
expense  by  increasing  the  percentage  of  reinforcement. 
It  is  important  that  fairly  rich  concrete  should  be  used 
in  all  cases  to  enable  the  posts  to  stand  exposure  and  to 
prevent  chipping. 

All  of  these  posts  measured  6  by  6  inches  at  the 
bottom  and  6  by  3  inches  at  the  top,  except  Nos.  29, 
30,  31,  32,  33,  and  34,  which  were  6  by  6  at  the 
bottom  and  3  by  3  at  the  top.  It  will  be  noticed  that  the 
saving  in  concrete  introduced  in  the  construction  of  these 
posts  is  accompanied  by  a  marked  decrease  in  strength 
as  compared  with  the  other  posts  similarly  reinforced. 
It  would  also  appear  that  the  twisted  wire  has  a  slight 


HOW  TO  USE  THEM 


375 


Table  II.   Showing  the  Strength  op  Reinforced 
Concrete  Fence  Posts. 


Kind  of  rein- 
forcement. 

Total  sectional  area  of  reinforcement. 
In  square  inches. 

Load  at  first  crack.    In  Pounds. 

Maximum  load.    In  Pounds. 

Equivalent  load  on  4-foot  cantilever 
at  first  crack.   In  Pounds. 

Equivalent  maximum  load  on  4-foot 
cantilever.   In  Pounds. 

Drawn  steel  rods 

0.08 

800 

1120 

218 

306 

.08 

820 

1145 

224 

313 

.08 

640 

1080 

175 

295 

.08 

795 

1040 

217 

284 

.08 

940 

1170 

257 

319 

.08 

740 

1075 

202 

293 

.19 

1140 

1280 

311 

349 

.19 

1170 

1885 

319 

515 

 do  

.19 

1020 

1950 

278 

532 

 do  

.19 

760 

1945 

207 

531 

 do  

.19 

820 

1925 

224 

526 

Twisted  fence  wire 

.06 

825 

935 

225 

255 

.06 

755 

905 

206 

247 

.06 

800 

940 

218 

257 

.06 

815 

935 

222 

255 

.06 

770 

980 

210 

268 

.06 

780 

975 

213 

266 

.13 

1550 

1920 

423 

524 

.13 

1275 

1670 

348 

456 

.13 

1200 

1830 

328 

500 

.13 

1500 

1955 

410 

534 

Barbed  wire 

.06 

980 

980 

268 

268 

 do  

.06 

820 

820 

224 

224 

 do  

.06 

590 

740 

161 

202 

do 

.06 

745 

745 

203 

203 

do 

.06 

590 

590 

161 

161 

 do  

.06 

550 

640 

150 

175 

do 

.06 

560 

635 

153 

173 

 do  

.06 

480 

530 

131 

145 

 do  

.13 

680 

1040 

186 

284 

 do  

.13 

840 

1010 

229 

276 

 do  

.13 

1280 

1515 

349 

414 

 do  

.13 

800 

1375 

218 

375 

Drawn  steel  rods 

.08 

Tested  by 

mpact  

 do  

.19 

do 

 do  

.19 

fin 

Twisted  fence  wire 

.06 

do... 

 do  

.06 

fin 

Form  of  reinforcement. 


376  CEMENTS  AND  CONCRETES 


advantage  over  the  barbed  wire  as  a  reinforcing  material, 
particularly  when  two  wires  are  used  in  each  corner  of 
the  post. 

As  stated  before,  it  is  impracticable  to  make  a  rein- 
forced concrete  fence  post  as  strong  as  a  wooden  post  of 
the  same  size,  and  this  is  more  especially  true  if  the  post 


has  to  withstand  the  force  of  a  sudden  blow  or  impact. 
In  order  to  study  the  behavior  of  these  posts  under  im- 
pact, a  number  of  them  were  braced,  as  illustrated  in 
No.  17,  and  subjected  to  the  blow  of  a  50-pound  bag  of 
gravel,  suspended  from  above  by  a  9-foot  rope.  The 
first  blow  was  delivered  by  deflecting  the  bag  so  as  to 
give  it  a  vertical  drop  of  1  foot,  and  for  each  successive 


HOW  TO  USE  THEM 


377 


blow  the  drop  was  increased  1  foot.  None  of  the  posts 
showed  any  signs  of  failure  under  the  first  blow.  Posts 
Nos.  14  and  20  cracked  under  the  second  blow,  and  failed 
under  the  third.  Post  No.  6  cracked  under  the  second 
blow,  which  cracked  open  under  the  third  blow,  causing 
a  momentary  deflection  of  5  inches.  Posts  Nos.  7  and  8 
each  developed  a  crack  under  the  second  blow,  but 
showed  no  further  signs  of  weakness  after  the  fifth  blow. 


Second  method  of  testing 
posts  by  impact. 

NO.  18. 


other  than  a  slight  opening  of  the  initial  crack.  In  each 
case  the  only  crack  developed  was  at  point  A.  Posts  6, 
7,  and  8,  which  cracked  but  did  not  fail  under  the  im- 
pact test,  were  further  tested,  as  indicated  in  No.  18,  by 
raising  the  small  end  and  allowing  them  to  drop  from 
successive  heights  at  1,  2^  3  and  4  feet.  Under  this  test 
a  number  of  cracks  developed,  but  in  no  case  did  the  re- 
inforcement fail. 

Although  it  might  appear  from  these  results  that  posts 
as  here  described  have  hardly  enough  strength  to  recom- 
mend them  for  general  use,  it  should  be  remembered  that 
ini  many  cases  fence  posts  are  not  subjected  to  impact. 


378  CEMENTS  AND  CONCRETES 


and  it  may  prove  more  economical  to  replace  from  time 
to  time  those  which  fail  in  this  way  than  to  use  wooden 
postS;  which,  being  subject  to  decay,  must  all  be  replaced 
sooner  or  later. 


-A. 

OS       /O      /S     20     2S    <30    <5S  -^S  so 


Diagram  showing  the  effect  of  clay  on  cement  mortars. 
NO.  19. 


Retempering. — Table  III.  illustrates  the  effect  of  re- 
tempering  Portland  cement  mortar.  The  mortars  used 
consisted  of  Portland  cement  and  crushed  quartzite  be- 
tween 1  and  2  millimeters  in  size,  mixed  in  different  pro- 


HOW  TO  USE  THEM 


379 


portions.  In  each  case,  after  the  initial  or  final  set  had 
taken  place,  sufficient  water  was  added  in  retempering  to 


TABLE  III. — Effect  of  Retempering  on  Cement  Mortars. 


Tensile  Strength,  in  Pounds  Per 
Square  Inch. 


Treatment  of  Mortar. 

1  Part 

IPart 

IPart 

Neat 

Cement, 

Cement, 

Cement, 

Cement. 

1  Part 

2  Parts 

3  Parts 

a 

odnu.  fj 

Sand,  c 

Qetnrl  rf 

i^cinu. 

651 

624 

527 

417 

Mortar  made  up  into  briquettes  . 
immediately  after  mixing  

650 
673 
634 

701 
624 
581 

493 
529 
480 

385 
421 
403 

679 

610 

492 

409 

Average   

657 

628 

504 

407 

671 

692 

589 

326 

Mortar  allowed  to  take  initial 

593 

670 

554 

349 

set,  then  broken  up  and  made  ^ 

644 

654 

559 

330 

into  briquettes  

633 

676 

534 

358 

724 

700 

532 

267 

Average   

653 

678 

554 

326 

455 

527 

492 

364 

Mortar  allowed  to  take  final 

522 

569 

491 

380 

set,    then    broken  up  and 

525 

587 

497 

361 

made  into  briquettes  

558 

566 

486 

315 

642 

568 

531 

345 

Average   

540 

563 

499 

353 

a  Initial  set,  1  hour  42  minutes;  final  set,  7  hours  15  minutes. 
h  Initial  set,  1  hour  30  minutes*  final  set,  7  hours  15  minutes, 
c  Initial  set,  2  hours;  final  set,  7  hours, 
d  Initial  set,  2  hours  20  minutes;  final  set,  7  hours. 


restore  normal  consistency.  The  briquettes  were  tested 
at  the  age  of  four  months. 


380  CEMENTS  AND  CONCRETES 


Some  Practical  Notes. — Spencer  B.  Newbury,  who  is 
an  authority  on  the  subject,  says  *^that  the  making  of 
good  cement  concrete  is  a  comparatively  simple  matter, 
and  yet,  like  most  simple  operations  in  engineering,  there 
is  a  right  way  and  a  wrong  way  of  doing  it.  Probably 
nine-tenths  of  the  concrete  work  done  falls  far  short  of 
the  strength  it  might  develop,  owing  to  the  incorrect  pro- 
portions, use  of  too  much  water,  and  imperfect  mixing. 
All  authorities  are  agreed  upon  the  importance  of  thor- 
ough mixing  and  the  use  of  the  minimum  quantity  of 
water  in  all  classes  of  concrete  work.  The  matter  of  cor- 
rect proportions  of  cement,  sand,  broken  stones,  etc.,  is 
one  which  requires  some  thought  and  calculation,  and  by 
proportioning  these  ingredients  correctly  an  immense 
saving  in  cost  and  increase  in  strength  can  easily  be  se- 
cured. 

The  chief  object  in  compounding  concrete  is  to  pro- 
duce a  compact  mass,  as  free  as  possible  from  pores  or 
open  spaces;  in  short,  to  imitate  solid  rock  as  closely  as 
possible.  Cement  is  the  essence  of  rock''  in  portable 
form,  and.  by  its  judicious  use  granular  or  fragmentary 
materials  may  be  bound  together  into  solid  blocks  of  any 
desired  size  and  shape,  which  in  strength  and  wearing 
qualities  are  at  lea'st  equal  to  the  best  stone  that  comes 
from  the  quarries.  Cement  is,  how^ever,  very  costly  in 
comparison  with  the  other  ingredients  of  concrete,  and 
must  not  be  used  wastefully.  A  little  cement,  judi- 
ciously used,  is  better  than  a  large  quantity  thj'own  in 
recklessly,  as  a  little  study  of  the  principles  involved 
will  plainly  show. 

To  produce  a  compact  mass  from  fragmentary  ma- 
terials, the  voids  must  be  filled.  Imagine  a  box  holding  1 
cubic  foot.   If  this  were  filled  with  spheres  of  uniform 


HOW  TO  USE  THEM 


381 


size,  the  voids  or  open  spaces  would  be  one-third  the  total 
volume,  or  33  1-3  per  cent.,  with  spheres  of  various  sizes, 
as,  for  example,  from  large  marble  down  to  fine  shot,  the 
voids  would  be  much  less,  and  it  would  theoretically  be 
possible,  by  the  use  of  spheres  of  graded  sizes,  from  the 
largest  down  to  dust  of  infinite  fineness,  to  fill  the  box 
completely,  so  that  there  would  be  no  voids  whatever.  In 
practice  it  is  well  known  that  the  use  of  materials  of 
varying  fineness  gives  the  best  concrete,  since  the  voids 
are  much  less  than  in  materials  composed  of  pieces  of 
uniform  size.  Hence  the  common  practice  of  making 
concrete  with  cement,  sand,  and  broken  stone,  instead  of 
with  cement  and  sand,  or  cement  and  stone  only.  The 
sand  fills  the  voids,  and  if  the  proportions  are  correct,  a 
practically  solid  mass  results.  As  an  example  of  this, 
the  writer  found  the  briquettes  of  cement  with  three 
parts  of  sand  and  four  parts  gravel  showed  higher  ten- 
sile strength  at  28  days  than  those  made  with  three  parts 
sand  only. 

The  following  table  gives  the  relative  weights  of  a 
given  volume  of  different  materials,  and  also  the  per- 
centage of  voids,  as  determined  by  the  writer.  The  ma- 
terials were  shaken  down  in  a  liter  measure  by  giving 
one  hundred  taps  on  the  table,  and  weighed.  In  the  case 
of  the  broken  stone  a  larger  measure  was  used.  The 
voids  were  calculated  from  the  specific  gravity. 

Comparison  of  the  three  different  grades  of  Sandusky 
Bay  sand  shows  how  greatly  the  percentage  of  voids 
varies  with  the  proportion  of  fine  and  coarse  grains  pres- 
ent. The  first  is  the  natural  sand,  not  screened,  as 
pumped  up  by  the  sand  sucker  from  the  bottom  of  the 
bay,  and  contains  a  large  amount  of  fine  gravel.  The 
second  is  the  same,  passed  through  a  20-mesh  screen  to 


382  CEMENTS  AND  CONCRETES 


remove  the  coarse  particles.  It  will  be  seen  that  this 
operation  increases  the  proportion  of  voids  from  32  to 
38  per  cent.  The  third  is  the  same  sand  passing  a  20- 
mesh  and  retained  on  a  30-mesh  screen,  thus  brought  to 
the  fineness  of  the  '^standard  sand"  used  in  cement  test- 
ing. This  shows  40.7  per  cent,  of  voids,  owing  to  the  uni- 
form size  of  the  grains.   The  same  relation  is  seen  in  the 


WEIGHT   OF   UNIT   MEASURE  AND   PERCENTAGE   OF   VOIDS  IN 
VARIOUS  MATERIALS. 


Per  Cent 
of 
Voids. 


Portland  cement  

Louisville  cement  

Sandusky  Bay  sand,  not  screened  

Sandusky  Bay  sand,  through  20-mesh 

screen   

Sandusky  Bay  sand,  20-30  mesh  (standard 

sand)  

Gravel,      to  %  inch  

Gravel,      to  inch  

Marblehead  broken  stone  (chiefly  about 

egg  size)  


82.3 

38.5 

40.7 
42.4 
35.9 

47.0 


two  grades  of  gravel  given  in  the  table,  that  containing 
finer  grains  showing  much  the  lower  percentage  of  voids. 
These  figures  illustrate  the  imprudence  of  screening 
any  of  the  materials  used  in  making  concrete.  The  pres- 
ence of  clay  in  sand  is,  however,  objectionable,  not  be- 
cause of  its  fine  state  of  subdivision,  but  because  the 
clay  coats  the  sand  particles  and  prevents  the  adhesion 
of  the  cement.  Such  sand  might  be  improved  by  wash- 
ing^ but  probably  not  by  screening.  It  has  been  found 


HOW  TO  USE  THEM 


383 


that  cement  which  has  been  ground  to  dust  with  an  equal 
amount  of  sand  goes  much  further  when  used  for  con- 
crete than  the  same  quantity  of  cement  when  used  in 
the  ordinary  way.  This  is  doubtless  owing  to  the  fact 
that  the  sand  dust  aids  in  filling  the  voids.  It  is  also 
well  known  that  slaked  lime,  when  added  to  cement  mor- 
tar, greatly  increases  the  strength  of  mixtures  poor  in 
cement. 

From  the  figures  given  in  the  above  table  the  compo- 
sition of  a  theoretically  perfect  concrete  may  readily  be 
calculated.  The  existence  of  voids  in  the  cement  may  be 
disregarded,  since  in  the  process  of  hardening  the  cement 
sends  out  crystals  in  all  directions,  completely  encrusting 
the  sand  particles  and  practically  filling  all  the  voids 
which  the  cement  itself  contains.  Examination  of  a 
well-hardened  briquette  of  cement  with  3  parts  sand, 
after  breaking,  with  the  aid  of  a  lens,  will  show  this 
clearly 

Suppose,  for  example,  we  wish  to  make  the  best  pos- 
sible concrete  from  Portland  cement  with  the  sand  and 
gravel  given  in  the  above  table.  We  should,  of  course, 
choose  the  unscreened  sand  and  gravel  as  containing 
the  least  proportion  of  voids.  One  hundred  measures  of 
gravel  would  require  35.9  measures  of  sand.  As  the 
sand  contains  32.3  per  cent,  of  voids,  we  require  32.3 
per  cent,  of  35.9,  or  11.6  measures  of  cement.  The  pro- 
portions would,  therefore,  be :  Cement,  11 ;  sand,  3,  and 
gravel,  9.  It  is  customary,  however,  to  increase  the  pro- 
portion of  mortar  (cement  and  sand)  by  about  15  or  20 
per  cent.,  in  order  that  the  coarser  materials  may  be 
completely  coated  with  the  finer  mixture.  Making  this 
addition,  we  find  the  concrete  proportions  to  be :  Cement, 
1 ;  sand,  2.8 ;  gravel,  7.   Allowance  must  also  be  made  in 


384  CEMENTS  AND  CONCRETES 


practice  for  imperfect  mixing;,  since  the  materials  can 
never  be  distributed  in  a  perfectly  uniform  manner. 
Practically,  with  these  materials,  a  concrete  of  cement 
1,  sand  2%,  and  gravel  6,  would  probably  give  the  best 
result,  and  little  or  no  improvement  would  result  from 
increasing  the  proportion  of  cement. 

A  similar  calculation  shows  that  the  correct  propor- 
tions for  a  concrete  made  of  the  sand  and  broken  stone 
given  in  the  table  would  be  1  to  3  to  6 1^.  Increasing 
the  amount  of  cement  and  sand  by  20  per  cent.^  w^e  have 
1  to  3  to  51/^.  Probably  1  to  2i/2  to  5  would  be  found  to 
give  the  best  results  in  practice.  The  determination  of 
the  voids  in  the  sand,  gravel  and  broken  stone  used  is 
of  the  greatest  value  in  adjusting  the  proportions  of 
concrete. 

The  simplest  method  of  determining  this  in  the  case  of 
gravel  and  broken  stone  is  to  have  a  metal  box  made  of 
1  cubic  foot  capacity ;  this  is  filled  with  the  material  to 
be  tested,  well  shaken  down  and  struck  off  level.  The 
box  and  contents  are  then  weighed.  Water  is  now 
poiured  in  until  it  rises  even  with  the  surface,  and  the 
total  weight  again  taken.  The  difference  in  the  weights 
is  the  weight  of  the  water  filling  the  voids  of  the  ma- 
terial. Now  1  cubic  foot  of  water  weighs  64-4-10  lbs., 
and  from  the  weight  of  the  water  found  the  percentage 
of  voids  can  be  simply  calculated.  For  example,  in  one 
experiment  the  box  and  broken  stone  weighed  88  lbs. 
After  filling  the  spaces  in  the  stone  with  water  the 
weight  was  1171/2  lbs.,  a  difference  of  29^/2  lbs.  The 
percentage  of  voids  is,  therefore,  29^/2x100  divided  by 
62.4  equals  47  per  cent. 

In  the  case  of  sand  this  method- will  not  answer,  as  it 
ig-;  difficult  to  completely  fill  the  voids  of  the  sand  by 


HOW  TO  USE  THEM 


385 


adding  the  water.  The  voids  can,  however,  be  readily 
calculated  from  the  weight  of  a  cubic  foot  and  the  spe- 
cific gravity.  The  specific  gravity  of  quartz  sand  is 
about  2.65.  A  cubic  foot  of  sand,  free  from  voids,  would 
therefore  weigh  2.65x62.4  equaling  165.4  lbs.  The 
weight  of  a  cubic  foot  of  sand,  well  shaken  down,  was, 
however,  found  to  be  only  112  lbs.,  a  difference  of  53.4 
lbs.  The  proportion  of  voids  was,  therefore,  53.4x100 
divided  by  165.4  equals  32.3  per  cent.  .  The  percentage 
in  voids  in  clean  natural  sand  does  not  vary  greatly,  and 
may  be  taken  as  33  to  35  per  cent,  for  coarse  and  35  to 
38  per  cent,  for  fine  sand. 

We  have  already  seen  that  with  the  materials  above 
described,  concrete  composed  of 

Cement  1,  sand  2^/^,  gravel  6,  or 

Cement  1,  sand  2%,  broken  stone  5 
by  measure,  will  be  practically  compact  and  non-porous, 
and  that  there  is  no  object  in  increasing  the  proportion  of 
cement.  Such  concrete,  if  made  from  Portland  cement, 
will,  however,  be  rather  expensive,  requiring  about  one 
barrel  of  cement  (equals  3^/2  cubic  feet)  for  every  cubic 
yard.  This  is  unnecessarily  good  for  ordinary  work,  and 
will  only  be  required  for  foundations  of  engines  and 
other  heavy  machinery,  in  which  the  best  possible  result 
must  be  secured  regardless  of  cost.  In  cheaper  concretes 
the  relative  proportions  of  sand  and  broken  stone  should 
be  the  same,  as  determined  by  the  voids  in  the  coarser 
materials,  while  the  proportion  of  cement  may  be  varied 
according  to  the  required  conditions  of  quality  and  cost. 
Most  excellent  concrete  may  be  made  by  using : 

Portland  cement  1,  sand  7,  stone  or  gravel  14. 

Here  are  specimens  of  these  two  concretes,  taken  from 
trial  blocks  laid  Oct.  1,  1894,  to  determine  the  best  pro- 


386  CEMENTS  AND  CONCRETES 


portion  for  the  foundation  of  brick  pavement.  The 
richer  of  the  two,  1-5-10,  is  certainly  good  enough  for 
any  purpose,  even  for  engine  foundations.  A  cubic  yard 
of  such  concrete  requires  about  %  barrel  of  cement ;  the 
total  cost  of  the  cement^  sand  and  stone  is  about  two 
dollars  per  cubic  yard.  This  is  no  more  expensive  than 
concrete  made  from  Louisville  cement  with  2  of  sand 
and  4  of  broken  stone,  and  is  immensely  superior  to  the 
latter  in  strength. 

The  following  table  shows  the  results  obtained  in 
Germany  by  R.  Dykerhoff  in  determining  the  crushing 
strength  of  various  concretes.    The  blocks  used  were 
inches  square,  and  were  tested  after  one  day  in  air  and 
27  days  in  water. 


Proportions  by  Measure. 

Strength  under  Compressionc 
Pounds  per  Square  Inch. 

Portland 
Cement. 

Sand. 

Gravel. 

1 

2 

2125 

1 

2 

3 

2747 

1 

2 

5 

2887 

1 

5 

978 

1 

8 

1383 

1 

3 

5 

1632 

1 

3 

6X 

1515 

1 

4 

1053 

1 

4 

5 

1273 

1 

4 

sX 

1204 

These  figures  prove  the  statement  already  made,  that 
mixtures  of  cement  and  sand  are  strengthened,  rather 
than  weakened,  by  the  addition  of  a  suitable  quantity 
of  gravel.   It  will  be  noticed  that  the  mixture — cement  1, 


HOW  TO  USE  THEM 


387 


sand  2,  gravel  5 — is  actually  stronger  than  cement  1, 
sand  2,  without  gravel.  The  same  is  shown  in  the  mix- 
tures 1  to  3  and  1  to  4. 

In  estimating  the  amount  of  material  required  to  pro- 
duce a  given  volume  of  concrete,  it  may  be  stated  that 
when  very  strongly  rammed  into  place  the  volume  of 
concrete  obtained  frcm  correct  proportions  of  the  ma- 
terials will  be  about  10  per  cent,  more  the  volume  1  cubic 
foot  cement,  2^^  cubic  feet  sand,  and  5  cubic  feet  stone, 
and  will  therefore  yield  about  5"^^  cubic  feet  concrete. 

Another  Concrete  Stairway  and  Steps. — A  good  stair- 
case is  one  of  the  essential  features  in  a  building.  The 
safety  and  convenience  of  persons  using  a  staircase  are 
not  only  affected  by  the  due  proportions  and  arrange- 
ments of  the  steps,  but  by  the  strength  and  fire-resisting 
properties  of  the  materials  employed,  and  the  manner  of 
construction.  The  w^ells  are  in  many  cases  too  small, 
out  of  proportion  to  the  structure,  which  necessitates 
dangerous  winders,  tiring  high  risers,  narrow  treads,  or 
insufficient  headway.  Some  architects  w^hen  designing  a 
staircase  pay  little  attention  to  the  practicability  of  con- 
struction. What  may  seem  easy  in  theory  or  on  paper 
is  often  found  impracticable  or  unnecessarily  difficult 
when  reduced  to  actual  practice.  The  errors  of  omission 
and  commission  are  left  for  the  workmen  to  contend 
with  and  overcome  as  best  they  may  at  the  employer's 
expense.  Happily  such  cases  are  few,  the  majority  of 
architects  supplying  figured  drawings,  which  are  not 
only  a  help  and  guide  to  the  workmen,  but  also  ensure 
a  practical  staircase  in  due  proportion  and  without  un- 
necessary expense.  Staircases  should  be  spacious,  light, 
and  easy  of  ascent.  It  is  generally  admitted  that  a  12 
inch  tread  and  a  6  inch  rise  is  the  most  convenient,  and 


388  CEMENTS  AND  CONCRETES 


that  no  tread  should  be  less  than  8  inches  or  more  than 
16  inches,  and  no  rise  less  than  4^/2  inches  and  more  than 
7  inches.  According  to  Blondel,  the  rise  should  be  re- 
duced y2  inch  for  every  inch  added  to  the  tread,  or  the 
tread  reduced  by  1  inch  to  every  ^  inch  added  to  the 
riser,  taking  a  12  inch  tread  and  a  6  inch  rise  as  the 
standard.  Treads  may  be  increased  by  means  of  a  nos- 
ing, which  usually  projects  from  1  inch  to  II/2  inches. 
Nosing  not  only  gives  more  available  space  for  the  tread, 
but  also  affords  some  advantage  to  persons  going  down 
stairs,  as  the  heel  cannot  strike  against  the  rising.  In 
setting  out  a  flight  of  stairs,  the  tread  of  the  steps  are 
measured  from  riser  to  riser.  Where  practicable,  the 
number  of  steps  from  landing  to  landing  should  be  odd, 
because  Avhen  a  person  begins  to  ascend  with  the  right 
foot  first  (as  most  people  do)  he  should  end  with  the 
same  foot.  Eectangular  steps  are  called  fliers.  Wind- 
ers, being  narrowed  at  one  end,  are  always  more  in- 
convenient and  dangerous  than  straight  steps,  and 
should  not  be  used  for  public  buildings  or  other  places 
where  there  is  a  crowded  traffic.  Winders  are  also 
more  expensive  to  construct.  They  are,  however,  un- 
avoidable in  circular  staircases,  also  in  some  instances 
in  angles,  where  a  quarter  or  half  space  landing  would 
not  give  the  desired  rise.  Winders  should  be  so  made 
that  the  tread  6  inches  from  the  end  of  the  narrow 
point  should  be  wide  enough  to  step  upon  without  dan- 
ger of  slipping.  No  stairs  should  be  less  than  three 
feet  from  the  wall  to  the  hand-rail.  A  width  of  3  feet 
6  inches  will  allow  two  persons  to  walk  arm  in  arm  up  or 
down  stairs.  A  width  of  4  feet 6 inches  is  generally  used; 
this  gives  plenty  of  space  for  two  persons  to  pass  each 
other.   No  hard  and  fast  rules  can  be  laid  down  for  the 


HOW  TO  USE  THEM 


389 


size  of  treads  and  risers,  as  they  are  regulated  more 
or  less  by  the  size  of  the  well  and  the  height  from  floor 
to  floor.  Too  few  steps  in  a  flight  are  as  bad  as  too 
many.  There  should  not  be  less  than  three.  Long 
straight  flights  of  steps  are  tiring  and  dangerous.  The 
straight  line  of  length  should  be  broken  by  landings, 
so  that  there  may  not  be  more  than  eleven  continuous 
steps.  Landings  give  ease  in  ascending  and  safety 
when  descending.  No  landing  should  be  less  in  length 
than  the  width  of  the  staircase.  The  staircases  in  the 
pre-Elizabethan  style  were  usually  plain,  dark  and  in 
long  narrow  flights ;  but  with  the  Elizabethan  archi- 
tecture came  in  a  more  commodious,  light  and  decora- 
tive style.  Wood  stairs  are  often  enriched  with  plaster 
work,  the  soffits  being  panelled  with  plaster,  and  the 
strings  adorned  with  composition  or  plaster  enrich- 
ments. Stone  stairs  are  also  frequently  enriched  with 
plaster  mouldings  in  the  angles  of  the  soffits  and  walls.. 
External  steps  and  landings  are  usually  made  with  a 
fall  of  ^4  inch  to  the  foot  to  allow  rain  to  fall  off. 

Cast  Concrete  Stairs. — Concrete  is  now  fast  super- 
seding stone,  wood  and  iron  for  staircase  construction, 
where  strength,  durability  and  economy  and  fire-resist- 
ing properties  are  required.  Cast  concrete  stairs  were 
first  introduced  nearly  sixty  years  ago.  The  stairs 
Avere  cast  in  single  steps,  or  in  treads  or  risers,  and 
fixed  in  the  same  way  as  natural  stone.  Square  and 
spandrel  steps,  risers  and  treads  are  cast  in  wood 
moulds;  circular  steps  and  curtails  in  plaster  moulds. 
Spandrel  steps  should  have  the  wall  or  ^^taiP'  end 
formed  square,  and  about  4^/2  inches  deep,  to  give  a 
better  bed  and  bond  in  the  wall.  A  good  mixture  is  3 
parts  of  granite  or  slag  chippings  and  1  of  Portland 


390  CEMENTS  AND  CONCRETES 


cement,  ganged  stiff,  and  well  rammed  into  the  monlds. 
When  set  they  are  removed  from  the  monlds,  air  dried, 
and  placed  in  water  or  a  silicate  bath,  and  treaded  in 
a  similar  way  to  that  described  for  slabs.  For  long 
steps  pieces  of  T  iron^  or  iron  pipes,  are  sometimes  in- 
serted in  the  centre  of  the  concrete  while  being  cast. 
The  iron  is  not  actually  required  to  strengthen  con- 
crete properly  made,  but  is  used  to  give  a  temporary 
strength  to  the  cast  while  it  is  green,  so  as  to  allow 
more  freedom  and  security  in  handling  the  cast  when 
it  is  being  taken  from  the  mould  and  moved  about  till 
permanently  fixed.  Landings  are  cast  in  a  similar  way, 
but  unless  very  small,  they  are  best  done  in  situ.  I 
have  made  landings  up  to  40  feet  superficial,  but  owing 
to  the  cost  of  transit,  hoisting  and  fixing  they  were 
not  profitable. 

Tests  of  Steps —The  following  examples  show  the 
strength  of  concrete  steps :  In  Germany,  when  con- 
structing a  concrete  stair,  with  square  steps  3  feet  4 
inches  long,  and  6-inch  tread,  and  6i/2-inch  rise,  and 
one  end  set  8  inches  into  the  walls,  four  steps  were  sub- 
mitted for  trial,  and  5,940  lbs.  weight  of  iron  were 
gradually  piled  on  them.  The  steps  showed  no  signs 
of  fracture,  but  no  more  weight  could  be  put  on  be- 
cause the  masonry  began  to  yield.  The  load  was  left 
on  three  days,  and  the  steps  remained  unaffected.  Al- 
though numerous  tests  have  been  made  of  concrete 
floors  and  blocks,  few  have  been  made  for  concrete 
steps.  The  following  may  be  given  as  a  reliable  one: 
The  steps  were  about  6  feet  long,  11-inch  tread  and 
6-inch  rise.  Every  step  was  tested  in  the  presence  of 
the  foreman  concreter  and  author.  The  steps  were 
supported  at  both  ends,  and  weighed  with  a  distribu- 


HOW  TO  USE  THEM 


391 


tive  load.  The  majority,  which  were  matured  by  age, 
passed  the  specification  standard. 

Concrete  Stairs  Formed  'Hn  Situ,^^ — Concrete  stairs 
are  an  outcome  of  stairs  built  with  cast  concrete  steps. 
Stairs  formed  in  situ  were  introduced  in  1867.  The 
idea  was  suggested  by  the  use  of  reverse  moulds  for 
fibrous  plaster  work,  and  in  the  formation  of  concrete 
dormer  windows  made  in  situ  on  some  mansions.  The 
step  landings  and  the  wall  bond,  being  a  monolith 
structure,  were  to  a  certain  degree  self-supporting. 
They  tend  to  strengthen  instead  of  to  weaken  the 
walls.  Architects  generally  supply  drawings  of  the 
intended  staircase,  but  as  there  is  often  a  differ- 
ence in  the  size  of  the  details  of  the  actual  work  and 
the  drawings^  it  is  necessary  that  the  workman  should 
have  a  practical  knowledge  of  setting  out  the  height'' 
and  ^^go"  for  the  pitch  board,  to  suit  the  landings  and 
the  well  of  the  staircase,  and  ensure  the  necessary  head- 
room. 

Setting  Out  Stairs —A  correct  method  of  setting  out 
the  framing  for  concrete  stairs  is  of  primary  import- 
ance. The  height  of  a  stair  is  the  length  of  a  per- 
pendicular line  drawn  from  the  upper  of  a  floor  to 
that  of  the  one  immediately  above  it.  The  ^^go"  is 
the  length  of  a  horizontal  line  drawn  along  the  centre 
line  of  the  flight  of  steps  or  stair  space.  The  exact 
height  and  widths  should  be  taken  on  a  rod,  which 
should  afterwards  be  used  for  setting  out  the  work. 
Never  work  without  this  rod,  as  it  is  quicker  and  more 
accurate  than  measuring  with  a  2-foot  rule.  There  are 
various  ways  of  getting  the  dimensions  of  treads  and 
rises.  The  following  is  a  simple  one  and  answers  for  most 
purposes.    The  height  and  go  are  taken  and  suitably 


392  CEMENTS  AND  CONCRETES 


divided.  For  example,  if  the  height  from  floor  line  to 
floor  line  is  9  feet  3  inches,  and  it  is  proposed  to 
make  each  rise  6  inches  high,  reduce  the  weight  to 
inches,  which  would  be  111 ;  divide  by  the  proposed 
height  of  each  step — 6  inches — the  quotient  will  be  18, 
giving  the  same  quotient  6  and  3-18.  If  there  are 
intermediate  landings,  or  half  spaces,  their  dimensions 
must  be  allowed  for.  The  size  of  the  tread  is  obtained 
by  dividing  the  ^^go"  by  the  number  of  steps.  The 
quotient  will  be  the  width  of  the  tread.  Great  care 
should  be  taken  in  setting  out  the  rods  and  pitch 
boards.  It  is  better  to  measure  thrice  than  to  cut  twice. 
When  the  string  line  is  marked  on  the  wall,  a  chase 
about  inches  deep  is  cut  into  the  wall.  It  is  not 
necessary  to  cut  the  chase  straight  at  the  soffit  line,  as 
it  is  apt  to  cut  into  a  half,  or  rather  a  whole  brick, 
and  leave  the  ends  loose.  The  irregular  line  of  chase 
below  the  soffit  line  can  be  made  solid  during  the  pro- 
cess of  filling  in  the  steps.  The  chase  should  be  cut 
as  the  work  proceeds.  Not  more  than  one  flight  at  a 
time  should  be  cut,  to  avoid  weakening  the  wall.  In 
some  instances  a  brick  course  in  sand  is  left  by  the 
bricklayers.  The  bricks  are  then  taken  out  as  the 
work  proceeds. 

Nosings  and  Risers, — ^Nosing  mouldings  should  be 
strong  and  bold.  A  simple  but  well-defined  moulding 
not  only  gives  greater  strength,  but  is  more  in  keep- 
ing with  its  purpose  than  one  with  numerous  or  small 
members.  Nosing  and  riser  moulds  are  best  formed 
in  two  parts,  the  nosing  moulds  being  one  part  and  the 
riser  board  the  other.  To  cut  them  out  of  the  solid 
would  not  only  be  expensive,  but  also  cumbrous  to  fix. 
They  can  be  run  ^t  most  saw  and  moulding  mills, 


HOW  TO  USE  THEM  393 


They  should  be  run  in  lengths  and  then  cut  and  mitred 
on  the  job.  Illustration  No.  20  shows  various  forms 
of  nosing.  Fig.  1  is  a  simple  nosing  for  common  work. 
Fig.  2  may  be  used  for  school  stairs^  etc.  Figs.  3  and 
4  are  well  adapted  for  a  good  class  of  work.  It  will  be 
seen  that  the  lower  edges  of  the  riser  boards  are 
splayed.  This  is  to  admit  the  shoe  of  the  running 
mould;  also  a  trowel  to  Avork  close  up  to  face  of  the 


Fig.  1.     Fig.         Fig.  3.      F^g.  4. 


1^ 


Sections  ob  Nosing 
"iviqulds  with  klser"  boards. 

NO.  20. 


concrete  riser  when  running  and  trowelling  off  the 
treads.  The  dotted  lines  indicate  the  line  of  tread. 
Nosing  moulds  are  cut  in  the  centre  of  the  section,  and 
afterwards  the  two  parts  are  held  in  position  with 
screws  while  the  steps  are  being  filled  in.  This  allows 
the  upper  part  to  be  unscrewed  and  taken  off  when  the 
stuff  is  nearly  set,  thus  allowing  more  freedom  to 
trowel  the  surface  of  the  tread;  also  to  make  a  better 
joint  while  the  stuff  is  green,  and  at  the  part  that  is 
cast  and  the  part  to  be  trowelled.  The  joint  in  the 
nosing  mould  leaves  a  thin  seam  which  is  easily  cleaned 
off,  w^hereas  the  joint  of  the  tread  and  nosing  is  not 
only  seen  more,  but  is  also  more  difficult  to  make  good. 


394  CEMENTS  AND  CONCEETES 


Illustration  No.  21  shows  the  mould  and  joint  and 
screws  for  fixing  same. 

Framing  Staircases. — The  wood  framing  for  con- 
crete stairs  differs  from  and  is  partly  the  reverse  to 
that  used  for  wood  stairs.  The  nosings  are  formed  the 
reverse  of  the  moulding,  and  the  whole  framing  is  so 
constructed  that  it  forms  a  mould  to  cast  all  the  steps 
and  landings,  from  floor,  in  monolithic  form,  or  one 
piece.    When  the  positions  of  half  spaces  or  other 


Jointed  Nosing  Mould 
WIQTH  KisER  Board. 
NO.  21. 

landings  are  set  out  on  the  walls,  strong  planks  are 
fixed  on  edges  so  as  to  give  fixing  joints  for  the  car- 
riage and  outer  strings.  The  strings  are  then  fixed 
to  act  as  guides  for  fixing  the  centring,  risers  and  nos- 
ing moulds.  Where  practicable,  the  outer  string  shoidd 
be  so  arranged  in  the  fixing  that  it  can  be  taken  off 
after  the  concrete  is  firm  without  disturbing  the  cen- 
tring. This  allows  the  returned  ends  of  the  steps  to 
be  cleared  off  while  the  work  is  green.  The  carriage 
boards  are  fixed  from  landing  to  landing.  Illustra- 
tion No.  22  shows  the  forms  and  positions  of  the  vari- 


396  CEMENTS  AND  CONCRETES 


ous  parts,  with  their  names.  BuUnoses  or  curtails  and 
circular  parts  of  nosings  are  formed  in  plaster  moulds, 
which  are  run  with  several  reverse  running  moulds. 

Staircases  between  walls  are  more  simple  than  open 
staircases;  therefore  they  are  more  eas}^  to  frame  up. 
The  string  boards  are  cut  to  the  reverse  of  that  used 
for  wood  stairs.  A  string  is  cut  for  each  wall.  The 
riser  boards  are  then  fixed  to  the  wall  strings.  The 
centring  for  the  soffits  is  fixed  independently,  the 
boards  being  laid  on  fillets  which  are  nailed  on  each 
wall.  For  short  flights  of  steps  or  common  stairs,  such 
as  for  cellars,  etc.,  string  boards  may  be  dispensed  with. 
The  positions  and  sizes  of  the  risers,  treads,  soffits  and 
landings  are  first  set  out  and  marked  on  the  walls. 
Riser  fillets  are  then  nailed  on  the  walls,  taking  care 
to  keep  each  fillet  in  a  line  with  the  riser  mark,  and 
to  allow  for  the  thickness  of  the  riser  boards  which 
are  subsequently  nailed  on  the  inner  sides  of  the  fillets. 
Riser  boards  for  winders  are  generally  hung  on  long 
fillets  and  then  nailed  on  the  walls.  Long  fillets  ex- 
tending upwards  enable  the  work  to  be  easier  and  more 
strongly  fixed,  as  they  cover  more  brick  joints  than  if 
cut  to  the  exact  height  of  the  riser. 

Centring  for  Landings  and  Soffits, — Centring  for 
landings  and  the  soffits  of  stairs  should  be  made  strong 
and  true.  The  timber  should  be  well  seasoned,  to  pre- 
vent warping  or  shrinkage.  The  outer  angles  of  land- 
ings should  be  supported  by  strong  wood  props,  not 
only  to  carry  another  prop  for  the  landing  above.  AH 
centrings  should  be  made  perfectly  rigid,  to  stand  the 
weight  of  the  concrete  and  the  ramming.  Great  care 
should  be  taken  that  the  timber  framing  is  securely 
supported,  as  any  deflection  will  not  only  throw  the 


HOW  TO  USE  THEM 


397 


work  out  of  level,  but  will  also  tend  to  crack  the  con- 
crete. The  principal  props  should  be  cut  about  I/2 
inch  shorter  than  the  exact  height.  They  are  placed 
on  a  solid  bed.  the  %-inch  space  at  top  being  made 
up  with  two  wedges,  the  thin  ends  being  inserted  in 
opposite  directions  and  gently  driven  home  from  each 
side  until  the  exact  height  is  obtained.  If  it  is  dif- 
ficult to  get  the  top  of  the  prop,  the  wedges  can  be 
inserted  at  the  bottom.  The  use  of  the  wedges  will 
be  seen  when  the  centring  is  struck.  If  there  are 
winders  in  the  stairs,  the  centring  for  the  soffit  will  be 
more  or  less  circle  on  circle.  This  form  of  centring 
is  done  by  lathing,  with  1-inch  boards,  cut  to  a  taper, 
the  surface  being  made  fair  with  a  gauged  lime  and 
hair.  Rough  1%-inch  boards  are  used  for  the  centring. 
This  should  be  close-jointed.  Open  joints  or  sappy 
timber  act  as  a  sieve,  and  allow  liquid  cement  to  drip 
through,  thus  robbing  the  concrete  of  its  strength. 

Waterproof  Centring.ii — The  following  is  a  method 
that  has  been  used  with  marked  success  for  the  sof- 
fits of  stairs,  landings  and  the  ceilings  of  floors.  The 
initial  cost  of  preparing  is  small,  and  is  repaid  with 
interest  by  the  decreased  cost  ,of  setting  and  the  in- 
creased strength  and  solidity.  For  ordinary  work, 
such  as  w^arehouses,  etc.,  it  is  very  suitable,  as  a  fin- 
ished surface  is  formed,  and  no  setting  required.  It 
seems  strange  that,  when  casting  concrete  work  out  of 
a  wood  or  a  plaster  mould,  the  mould  is  seasoned,  and 
every  precaution  taken,  not  only  to  stop  suction,  but 
also  to  prevent  the  escape  of  liquid  cement;  but  when 
casting  a  large  surface  in  situ  (where  every  precau- 
tion should  be  taken  to  obtain  the  maximum  of 
strength),  any  kind  of  centring  (which  is  a  mould) 


398 


CEMENTS  AND  CONCRETES 


is  thought  good  enough,  if  only  sufficiently  strong  to 
carry  the  concrete  till  set.  I  am  aware  that  many 
workers  in  concrete  think  that  an  open  or  porous 
centring  is  a  benefit  instead  of  a  defect,  simply  be- 
cause it  affords  an  escape  for  excess  of  water.  But 
why  have  excess  of  water  at  all?  There  is  no  gain 
in  time  or  strength,  but  a  direct  loss  in  both  points. 
The  excess  water  descends  through  the  concrete  by 
force  of  direct  gravitation,  and  always  carries  a  cer- 
tain amount  of  liquid  cement  with  it  to  the  centring, 
leaving  the  aggregate  more  or  less  bare,  and  the  body 
of  the  concrete  weak.  A  part  of  the  liquid  cement 
also  oozes  through  the  joints  and  crevices,  which  leaves 
the  skin  of  the  concrete  bare  and  broken.  There  is 
no  reason  or  excuse  for  excess  water,  and  it  is  simply 
the  result  of  ignorant  or  careless  gauging,  which  is  not 
only  a  waste  of  time,  water  and  cement,  but  a  loss  in 
the  ultimate  strength,  and  the  cause  of  cracks.  Porous 
centring  is  also  a  dirty  process.  The  overhead  drip, 
drip,  is  neither  good  for  the  workmen  nor  the  material 
underneath. 

The  process  of  forming  the  rough  centring  boards 
watertight  is  simple  and  expeditious,  being  done  by 
laying  the  rough  board  surface  with  a  thin  coat  of 
gauged  plaster ;  and  when  the  centring  has  been  struck 
the  plaster  will  come  with  the  boards,  leaving  the  con- 
crete with  a  fair  face.  The  ramming  forces  a  certain 
amount  of  water  to  the  lower  surface  or  centring,  and 
this  is  so  close  and  fine  that  it  takes  an  exact  impress 
of  it ;  consequently  the  truer  and  smoother  the  centring 
the  truer  and  smoother  the  concrete  surface.  The  film 
of  water  indurates  the  skin  of  the  concrete  and  prevents 
surface  or  water  cracks.    It  will  be  noticed  when  filling 


HOW  TO  USE  THEM 


399 


in  dry  or  porous  plaster  moulds  that  the  concrete  cast 
produced  has  a  surface  either  friable  when  newly  cast, 
or  when  dry  the  surface  is  full  of  small  water  lines, 
like  a  map,  or  a  broken  spider's  web.  This  is  owing 
to  the  suction  caused  by  the  porous  nature  of  the  mould 
and  the  water  escaping  through  the  weak  or  open  parts 
leaving  corresponding  lines  on  the  concrete  surface. 
These  defects  are  obviated  by  using  waterproof  cen- 
tring. 

Where  fineness  of  finish  is  not  required,  such  as  ware- 
house floors,  the  surface  can  be  made  sufficiently  fair 
and  smooth  when  fiJling  in  the  concrete  without  sub- 
sequent setting.  The  plaster  is  laid  on  the  centring, 
and  made  fair  and  smooth,  and  then  the  surface  is 
saturated  with  water  to  correct  the  suction;  or  the 
surface,  if  dry,  may  be  brushed  over  with  a  thin  soap 
solution  to  j)i"event  adhesion.  On  this  surface  a  coat 
of  neat  cement  about  %  inch  is  laid,  and  on  this  the 
concrete  is  placed.  The  two  unite  in  one  body,  and 
when  set,  and  the  centring  struck,  the  plaster  sheet 
comes  with  the  boards,  leaving  a  smooth  surface.  This 
surface  can  be  made  in  color  by  lime  washing,  which 
will  also  give  more  light,  or  a  finished  white  surface 
can  be  obtained  by  substituting  parian  or  other  white 
cement  for  the  neat  Portland  cement.  The  concrete 
must  not  be  laid  until  the  white  cement  is  firm,  not  set, 
otherwise  the  concrete  will  force  its  way  in  thin  or 
soft  parts  and  disfigure  the  surface.  I  have  success- 
fully used  this  method  for  obtaining  a  finished  sur- 
face when  encasing  iron  girders  with  concrete  for  fire- 
proof purposes. 

Staircase  Materials. — With  regard  to  the  materials 
for  a  concrete  staircase^  no  one  who  intends  to  con- 


400  CEMENTS  AND  CONCRETES 


struct  them  substantially,  fireproof  and  economically, 
can  afford  to  use  common  substances,  when  by  judi- 
cious selection  and  for  a  trifling  additional  first  cost  a 
combination  of  materials  can  be  obtained,  which,  if 
not  (strictly  speaking)  fireproof,  is  at  least  the  most 
incombustible  constructive  compound  known.  This  is 
a  quality  of  the  most  vital  importance  in  modern  house 
construction.  Portland  cement  and  slag  cement  are 
the  best  known  matrices.  The  finer  Portland  cement 
is  ground,  the  greater  its  heat-resisting  powers.  Slag 
cement  is  lighter  than  Portland  cement,  and  its  fire- 
resisting  properties  exceed  those  of  both  gypsum  and 
Portland  cement.  But  as  its  manufacture  is  as  yet 
somewhat  limited,  and  its  strength  not  uniform,  ex- 
ceptional care  must  be  exercised  in  testing  its  general 
qualities  before  using  it  for  staircases.  Broken  slag, 
firebricks,  clinkers  and  pottery  ware  are  the  best  ag- 
gregates, being  practically  fireproof.  All  should  be 
clean,  and  in  various  graduating  sizes,  from  that  of  a 
pin's  head  to  that  of  a  walnut,  for  roughing  out  with. 
The  topping  should  be  the  same  as  that  described  for 
Eureka  paving. 

Filling  in  Stairs, — Before  gauging  the  materials, 
sweep  out  all  dust  in  the  interior  of  the  framing  and 
the  wall  chase  and  then  wet  the  latter,  and  oil  the 
woodwork.  If  the  wood  of  the  nosing  moulds  and 
risers  is  sappy  or  open  grained,  the  long  lengths,  be- 
fore being  cut  and  fixed,  should  be  made  smooth  and 
indurated  by  coating  with  a  solution  of  hot  paraffin 
wax.  The  smoother  and  less  absorbent  the  surface  of 
the  wood,  the  more  readily  and  cleaner  will  the  mould 
leave  the  cast  work.  Paraffin  also  renders  the  wood 
damp-proof,  thus  preventing  swelling  or  warping.  For 


HOW  TO  USB  THEM 


401 


ordinary  purposes  one  or  two  coats  of  paraffin  oil  will 
be  found  sufficient.  This  should  be  done  two  or  three 
hours  before  the  steps  are  filled  in^  so  as  to  allow  the 
oil  to  partly  dry  in  and  stop  the  pores  of  the  wood. 
If  the  wood  absorbs  all  the  oil,  and  has  a  dry  sur- 
face, brush  the  surface  again  with  paraffin,  using  a 
semi-dry  brush.  This  should  be  done  as  the  work  pro- 
ceeds. If  the  surface  is  over  wet,  the  oil  mixes  with 
the  cement,  thus  causing  a  more  or  less  rough  sur- 
face. Soap  solution  may  be  safely  used  for  rough 
concrete,  or  where  a  rough  surface  is  left  to  be  sub- 
sequently set.  In  the  latter  case  the  surface  must  be 
well  wetted  with  water  and  scrubbed  before  the  final 
coat  is  applied.  Soap  solution  may  also  be  used  for 
rough  framing,  such  as  soffit  boards,  but  soap  should 
not  be  used  for  fine  concrete  or  a  finished  surface, 
as  it  leaves  a  film  of  grease  which  has  a  tendency  to 
prevent  the  cement  adhering  when  clearing  up  or  mak- 
ing good  the  finished  surface.  As  the  work  of  filling 
proceeds,  the  surface  should  be  brushed  over  with  a 
slip,  that  iS;,  neat  cepaent,  to  fill  up  all  angles,  and 
obtain  a  surface  free  from  bulbs"  and  ragged  ar- 
rises. 

The  coarse  concrete  for  roughing  out  the  stairs  is 
composed  of  1  part  of  Portland  cement  and  3  parts  of 
coarse  fireproof  aggregate.  These  material-s  must  be 
gauged  stiff  and  laid  in  small  portions  of  about  a  pail- 
ful at  a  time,  taking  care  to  thoroughly  consolidate 
by  ramming  and  beating  with  a  wooden  mallet,  using 
a  wooden  punner  or  punch  to  get  into  the  angles  and 
deep  parts.  When  the  first  layer,  which  may  be  about 
3  inches  thick,  is  rammed,  another  layer  is  deposited 
and  rammed,  and  so  on  until  the  rough  stuff  is  within 


402 


CEMENTS  AND  CONCRETES 


%  inch  of  the  line  of  tread.  It  must  not  be  omitted  to 
brush  the  strings,  treads  and  nosing  moulds  with  slip 
as  the  work  proceeds.  This  is  most  effectually  done 
by  the  aid  of  a  tool-brush.  Care  must  be  exercised 
when  ramming  stairs  with  mallets  or  punches  that  the 
mallet  or  other  implement  used  is  not  too  large  or  too 
heavy,  for  it  would  most  likely  cause  the  framing  to 
bulge  out,  and  the  form  of  the  work  would  be  irre- 
trievably spoilt.  During  the  operation  of  ramming 
some  of  the  water  and  a  part  of  the  constituent  of  the 
cement  is  forced  upwards,  and  leaves  a  thin,  smooth, 
clayey  film  on  the  surface,  which  prevents  the  adhesion 
of  the  next  layer.  For  this  reason  the  successive  lay- 
ers should  be  deposited  before  the  previous  one  is  set, 
and  the  topping  should  be  laid  while  the  coarse  con- 
crete is  yet  green.  Too  much  stress  cannot  be  laid  upon 
the  importance  of  topping  the  rough  coat  while  it  is 
green.  This  is  one  of  the  secrets  of  success  of  solid 
and  strong  work,  so  no  more  rough  stuff  should  be  laid 
than  can  be  topped  before  the  rough  is  set. 

The  fine  stuff  for  the  topping  is  the  same  as  for 
Eureka  paving,  viz.,  1  part  of  cement  to  2  parts  of  fine 
aggregate,  gauged  firm  and  plastic.  The  tread  is  made 
level  and  fair  by  means  of  a  running  mould  so  formed 
that  it  bears  on  the  nosing  moulds  above  and  below  the 
tread.  The  mould  has  a  metal  plate  or  ''shoe"  fixed 
so  as  to  run  and  form  the  tread.  The  shoe  projects 
so  that  it  will  work  under  the  riser  board  close  up  to 
the  concrete  riser.  Illustration  No.  23  shows  a  sec- 
tion of  steps  with  the  mould  in  position;  also  a  sec- 
tion of  the  nosing  mould  and  soffit  boards  and  car- 
riage. The  end  of  the  slipper  next  to  the  wall  is  cut 
short  to  ^llow  the  mould  to  run  close  up  to  the  walL  A 


HOW  TO  USE  THEM 


403 


section  of  a  T  iron  is  shown  as  sometimes  used  as  an  in- 
ternal support.  Iron  is  used  for  long  steps,  or  where 
stairs  are  intended  for  heavy  traffic.  Iron  helps  to  sup- 


— Sections  of  Framing  of  Soffit  op  Stair,  Riser 
And  Noser  Mould,  with  Concrete  and  Tread  Run- 
king  Mould  in  Position. 

NO.  28. 


port  the  concrete  until  set;  it  is  placed  in  alternate 
steps,  or  in  every  third  or  fourth  step,  according  to  the 
length  of  step.    Ordinary  sized  steps  require  no  iron, 


404  CEMENTS  AND  CONCEETES 


unless  as  a  support  for  the  concrete  while  green,  and 
during  the  process  of  making. 

Finishing  Stairs. — When  the  treads  are  firm  after 
being  run,  the  upper  part  of  the  nosing  moulds  are 
removed,  the  surface  and  joists  trowelled  off.  The  ad- 
vantages of  having  the  nosing  mould  in  two  parts  will 
thus  be  seen,  as  it  allows  the  joint  at  this  most  notice- 
able part  to  be  neatly  cleaned  off  while  the  work  is 
green.  The  lower  part  of  the  mould  will  support  the 
concrete  nosing  during  the  finishing  of  the  tread  and 
until  the  concrete  is  set.  If  the  work  is  done  with  a 
nosing  mould  in  one  piece,  which  necessitates  its  being 
left  on  until  the  concrete  is  set,  the  joint  has  then  to  be 
filed  down  and  stopped,  and  however  well  done,  has  a 
patchy  appearance.  When  the  treads  are  finished,  and 
the  work  set,  but  not  dry,  the  riser  and  string  boards 
are  taken  off,  the  joints  made  good,  and  the  returned 
end  of  the  steps  cleaned  off.  If  the  stuff  has  been 
properly  gauged  and  rammed,  there  should  be  little 
or  no  making  good  required,  but  it  is  important  that 
if  necessary  it  should  be  done  while  the  work  is  green. 
A  thin  layer  of  neat  cement  will  not  adhere  on  a  dense 
and  dry  body  of  concrete.  The  only  way  to  obtain 
perfect  cohesion  is  to  cut  the  damaged  surface  out  to 
a  depth  of  not  less  than  ^4  inch,  then  thoroughly  wet 
it,  brush  the  surface  with  liquid  cement,  and  fill  it  in 
with  gauged  cement.  No  traffic  should  be  allowed  on 
the  treads  during  the  process  of  setting  and  harden- 
ing. The  work  is  further  protected  and  hardened  by 
covering  w^ith  sacks  kept  wet  for  several  days  by  fre- 
quent watering.  Where  there  are  several  flights  of 
stairs  to  construct,  there  should  not  be  less  than  three 
sets  of  strings  and  riser  boards,  which  will  enable  the 


HOW  TO  USE  THEM  405 


carpenter  to  fix  one  set  while  the  plasterers  are  filling 
in  and  cleaning  off  the  others. 

Non-Slippery  Steps. — Incessant  traffic  tends  to  make 
the  treads  of  steps  more  or  less  slippery.  In  order  to 
obviate  this,  the  surface  is  indented  with  a  concrete 
roller,  similar  to  that  used  for  some  kinds  of  paving. 
Another  way  is  to  form  three  or  four  V-shaped  grooves 
from  1  inch  to  2  inches  apart  on  the  treads  while  the 
concrete  is  moist.  Another  way  is  to  insert  leaden 
cubes  about  1  inch  square "  from  2  to-  3  inches  apart 
in  the  surface  of  the  treads.  Well-seasoned,  hard 
wooden  blocks,  about  the  same  size  as  the  lead  and 
fixed  in  a  similar  way,  keeping  the  end  grain  vertical, 
are  also  used  for  this  purpose.  India  rubber  and  cork 
cubes  may  also  be  used. 

Striking  Centrings. — This  should  not  be  attempted 
until  all  the  other  work,  with  the  exception  of  finishing 
the  soffits,  is  done.  It  will  be  understood  that  the 
framing  can  be  arranged  so  that  the  string  and  riser 
boards  can  be  taken  off  without  disturbing  the  soffit 
centring,  which  is  kept  up  as  long  as  possible.  The 
time  for  striking  centring  greatly  depends  upon  the 
class  of  cement  used,  the  manner  of  gauging  and  lay- 
ing the  concrete,  and  the  temperature;  but  generally 
speaking,  centring  should  not  be  struck  for  at  least 
ten  days.  A  stair  between  the  walls  can  be  struck 
much  sooner  than  one  having  only  one  bearing  by  which 
its  own  weight  is  carried.  I  have  seen  a  stair,  with 
steps  projecting  3  feet  6  inches  from  the  wall,  cleared 
of  all  supports  in  five  days  from  the  time  of  filling 
in ;  but  this  was  with  good  cement,  gauged  1  part  to  2 
of  aggregate,  and  in  warm  weather,  and  the  stair  was 
strengthened  with  T  iron. 


406  CEMENTS  AND  CONCRETES 


The  centring  and  framing  for  a  flight  of  stairs  should, 
where  practicable,  be  independent  of  other  stairs  above 
or  below,  so  that  they  can  be  struck  in  due  rotation. 
The  wedges  of  the  main  props  should  be  gradually 
withdrawn.  This  tends  to  avoid  the  sudden  jar  which 
otherwise  often  happens  when  the  centring  is  too  sud- 
denly struck.  The  sudden  removal  of  centring  and 
the  inflexible  nature  of  concrete  are  the  cause  of  body 
cracks.  The  damage  caused  by  the  sudden  jar  may 
not  be  seen  at  the  time,  but  it  will  be  eventually  devel- 
oped by  the  force  of  expansion,  which  always  finds  out 
the  weak  spots. 

Concrete  and  Iron. — Iron  pipes,  bars  and  T  pieces 
are  sometimes  used  with  concrete  stairs  where  the  steps 
are  long,  or  where  landings  have  little  support  from 
walls.  They  help  to  carry  the  dead  weight  until  the 
mass  is  thoroughly  set,  and  also  prevent  sudden  de- 
flection if  the  centring  is  struck  too  soon.  When  iron 
pipes  are  used  for  steps  they  should  go  right  into  the 
wall  chase.  Iron  T  pieces  are  used  for  long  landings. 
Care  must  be  taken  that,  if  the  iron  is  used,  no  part 
should  be  left  exposed.  It  must  be  embedded  in  the 
concrete  to  protect  it  from  oxidization  and  the  effects 
of  fire.  AVhen  iron  girders,  etc.,  are  partly  exposed, 
they  should  be  painted.  Iron  bars  or  pipes  are  occa- 
sionally used  to  strengthen  the  outer  strings  of  spandrel 
stairs.  The  iron  is  laid  in  the  moist  concrete 
near  and  along  the  string,  having  the  ends  projecting 
into  the  walls  or  landings.  Angle  irons  are  often  used 
for  unsupported  concrete  angles.  Iron  pipes,  bars  or 
joists  are  used  as  integral  supports  for  landings  and 
floors  having  unsupported  ends. 

The  tensile  strength  of  bar  iron  is  materially  in- 


HOW  TO  USE  THEM 


407 


creased  by  twisting.  A  bar  %  inch  square  with  three 
twists  per  foot  will  gain  about  50  per  cent,  in  tensile 
strength  when  embedded  in  concrete,  and  give  a  corre- 
sponding strength  to  the  concrete.  A  combination  of 
iron  and  concrete  is  of  special  service  where  space  is 
limited.  For  instance,  if  a  beam  or  landing  requires 
a  certain  thickness  to  carry  a  given  weight,  and  it  is 
inconvenient  or  difficult  to  obtain  that  thickness,  the 
requisite  degree  of  strength  with  a  reduced  thickness 
may  be  obtained  by  the  combination  of  both  materials. 
This  gives  the  combined  iron  and  concrete  a  useful  ad- 
vantage over  stone.  It  is  important  to  secure  the  full 
strength  of  the  iron,  and  that  none  be  lost  or  neutral- 
ized. In  order  to  obtain  the  full  strength  the  iron 
should  be  judiciously  placed.  Thus,  a  piece  of  iron 
surrounded  by  twenty  times  its  sectional  area  of  con- 
crete would  increase  the  weight-sustaining  power  of  the 
iron  in  the  centre  and  would  have  its  strength  in- 
creased about  twice.  If  the  same  quantity  of  iron  was 
placed  in  several  pieces,  so  as  to  throw  as  much  tensile 
strain  on  the  iron  as  possible,  the  strength  would  be 
increased  nearly  four  times.  In  order  that  none  of  the 
strength  be  lost  or  neutralized,  the  iron  should  be 
placed  near  the  lower  surface ;  if  fixed  higher,  they  are 
nearer  the  axis  of  neutral  stress,  and  are  correspond- 
ingly less  effective.  The  use  of  iron  in  concrete  is  in= 
valuable  for  many  constructive  purposes,  but  for  gen- 
eral work,  unless  as  a  temporary  aid  and  in  a  few  ex- 
ceptional cases,  it  is  unnecessary.  For  all  other  things 
being  equal,  the  huge  board  of  reserve  strength  in  good 
concrete  is  alone  sufficient  to  sustain  as  great  if  not 
a  greater  weight  than  that  sustained  by  natural  stone. 
No  other  artificial  compound  exceeds  the  strength  of  the 


408  CEMENTS  AND  CONCKETES 


natural  substance,  as  does  artificial  stone  composed  of 
Portland  cement  concrete. 

Setting  Concrete  Soffits. — The  soffits  of  stairs  and 
landings,  if  neat  cement  has  been  used  on  a  water- 
proof centring,  as  already  described,  only  require  a  lit- 
tle stopping  and  coloring,  but  for-  work  done  on  rough 
centring  a  setting  coat  has  to  be  laid.  This  is  usually 
done  with  neat  Portland  cement,  though  it  is  frequently 
gauged  with  lime  putty  to  make  it  work  more  freely. 
The  surface  should  be  well  roughened  and  wetted,  to 
give  a  key  and  obtain  perfect  cohesion.  It  requires 
great  care  and  time  to  make  a  good  and  true  surface 
with  Portland  cement  on  a  body  of  concrete,  espe- 
cially if  the  concrete  is  dry,  which  is  generally  the 
case  where  there  are  several  flights  of  steps  in  a  stair- 
case, and  the  setting  of  the  soffits  and  landings  are 
left  to  the  last  part  of  the  work.  I  have  obtained 
equally  good  results  by  using  Parian  or  other  white 
cements  for  setting  the  soffits  of  staircases.  When 
using  white  cements  for  this  purpose  it  is  better  to 
brush  the  concrete  surface  with  liquid  cement  before 
laying  the  gauged  cement.  The  laying  trowel  should 
follow  the  brush,  or  at  least  before  the  liquid  cement 
dries  in.  This  not  only  secures  better  cohesion,  but 
tends  to  prevent  the  setting  coat  peeling  when  trowel- 
ling it  off.  Soffits  are  sometimes  set  with  gauged  put- 
ty. This  is  like  putting  a  beggar  on  horseback,  and 
the  work  is  never  satisfactory. 

Fibrous  Concrete. — As  already  mentioned,  canvas 
and  other  fibrous  materials  may  be  advantageously 
used  with  Portland  cement  for  several  purposes.  Can- 
vas forms  a  good  ground  for  a  setting  coat  on  concrete 
surfaces.    It  gives  a  uniform  and  strong  key,  prevents 


HOW  TO  USE  THEM 


409 


surface  cracks,  and  the  final  coat  from  peeling.  Coarse 
canvas  cut  to  convenient  sizes  is  used.  It  is  laid  on 
the  centring,  and  held  in  position  with  tacks,  or  with 
the  same  kind  of  cement  as  intended  for  the  final  coat. 
The  canvas  is  then  brushed  with  liquid  cement,  and 
then  the  concrete  is  laid  while  the  canvas  is  moist,  so 
that  the  whole  will  form  one  compact  body.  When  the 
centring  is  struck,  the  fibrous  concrete  surface  is  rough- 
ened with  a  sharp  and  fine  drag,  so  as  to  raise  the 
fibre  of  the  canvas,  thus  giving  a  fine,  regular  and 
strong  key.  This  surface  requires  less  material  for  the 
final  coat  than  the  ordinary  concrete  surface.  If  tacks 
are  used  they  must  be  extracted  before  the  final  coat  is 
laid,  to  avoid  discoloration.  The  rough  concrete  and 
the  white  surface  coat  may  also  be  done  in  one  opera- 
tion. The  centring  is  made  fair  and  smooth,  and  then 
oiled  with  chalk  oil.  The  white  cement  is  gauged  stiff 
and  laid  on  the  centring.  Coarse  canvas  is  then  laid 
on  and  well  brushed  with  liquid  cement.  When  this 
is  firm  (but  not  set)  the  surface  is  again  brushed, 
and  then  the  concrete  is  laid.  The  concrete  is  deposited 
in  two  or  more  layers.  The  first  must  not  be  too  thick, 
taking  care  that  it  is  well  rammed  or  pressed  on  the 
moist  canvas  surface  without  disturbing  the  white  ce- 
ment. .After  the  centring  is  struck  any  defects  on 
the  surface  are  made  good.  The  surface  may  be  then 
left  white,  or  painted,  or  polished  as  required. 

Polished  Soffits, — Soffits,  landings  and  strings  of  con- 
crete stairs  that  are  finished  in  white  cement  may  be 
polished.  The  material  may  be  tinted,  or  left  in  its 
natural  white  or  creamy  color.  Polished  cement  work 
is  always  bright,  and  has  a  lustre  like  marble.  Be- 
ing durable  and  easily  cleaned^  it  is  more  sanitary  and 


410  CEMENTS  AND  CONCRETES 


cheaper  than  paint.  The  polishing  is  done  the  same 
way  as  described  for    white  work." 

Concrete  Staircases  and  Fibrous  Plaster, — Fibrous 
plaster  is  well  adapted  for  concrete  surfaces  when  an 
enriched  finish  is  desirable.  I  have  introduced  this 
material  for  decorating  the  soffits  of  steps  and  land- 
ings ;  also  the  strings  of  concrete  stairs.  By  this  method 
the  soffits  may  also  be  enriched^  and  strings  can  be 
panelled;  or  enriched  with  medallions  or  foliage,  as  re- 
quired. The  soffits  may  also  be  enriched  with  modelled 
work  done  in  situ^  with  some  of  the  white  cements,  or 
with  plaster  and  tow.  The  strings  may  be  decorated 
with  hand-wrought  gesso.  In  order  to  obtain  a  fixing 
or  keying  substance  that  will  receive  nails  or  screws 
to  sustain  the  fibrous  plaster,  a  rough  plan  of  the  de- 
sign, or  rather  the  fixing  points,  is  set  out  on  the  in- 
side of  the  centring  before  the  concrete  is  laid.  On 
these  plans  wood  plugs,  fillets  or  concrete  fixing  blocks 
are  laid,  and  held  in  position  with  nails,  plaster  or  ce- 
ment until  the  concrete  is  laid  and  set.  Care  must  be 
exercised  when  fixing  the  plugs  or  fillets  that  the 
centring  will  leave  freely  without  disturbing  the  plugs, 
etc. 

Dowel  Holes. — Cutting  dowel  holes  in  concrete  to 
receive  iron  or  wood  balusters  is  a  slow  and  tedious 
process.  The}^  are  best  formed  by  means  of  wooden 
plugs,  which  are  fixed  before  treads;  the  plugs  are 
driven  into  the  rough  concrete  before  it  is  set,  leaving 
them  flush  with  the  line  of  tread,  so  that  when  the 
topping  is  laid  they  will  not  be  in  the  way.  Plugs 
are  best  fixed  by  the  aid  of  a  wooden  gauge.  The 
gauge  is  made  the  same  thickness  as  the  topping,  the 
length  being  equal  to  the  distance  between  the  nosing 


HOW  TO  USE  THEM 


411 


mould  and  the  riser  boards  and  as  wide  as  will  admit 
of  plug  holes  and  the  plugs  to  be  driven  through.  The 
plugs  are  made  a  little  larger  than  the  baluster  ends 
to  allow  for  the  lead.  The  gauge  is  laid  on  the  rough 
concrete,  using  the  returned  nosing  as  a  guide,  and  then 
driving  the  plugs  flush  with  the  top  of  the  gauge. 
The  gauge  is  then  lifted  up  and  laid  on  the  next  step, 
and  so  on  until  the  finish.  This  method  is  accurate 
and  saves  measuring  and  marking  the  position  of  each 
hole  on  every  step.  When  balusters  are  fixed  on  the 
ends  of  the  steps,  the  plugs  are  fixed  on  the  inside  of 
the  outer  string.  The  plugs  are  generally  left  in  until 
the  balusters  are  ready  for  fixing.  A  ready  method 
for  forming  lewis"  holes  or  other  undercut  sink- 
ings in  concrete  is  performed  by  casting  wedge-shaped 
blocks  of  plaster  of  the  required  form  and  size,  and 
then  laying  them  in  the  desired  positions  while  the 
concrete  is  soft.  When  the  concrete  is  set,  the  plaster 
blocks  can  then  be  easily  cut  out,  leaving  the  under- 
cut sinking  as  desired. 

Summary  of  Staircases  Constnicted  ^^in  Situ.'^ — It 
will  be  seen  from  the  foregoing  that  the  operations  em- 
ployed in  the  construction  of  concrete  staircases  formed 
m  situ  are:  (1)  setting  out  the  stairs  and  landing;  (2) 
fixing  the  wood  framing;  (3)  gauging  the  materials  and 
filling  in;  (4)  removing  the  framing;  (5)  cleaning  up 
the  treads,  risers  and  strings;  (6)  striking  the  soffit 
centring  and  finishing  the  soffits;  (7)  protecting  and 
wetting  the  work  until  set  and  hard. 

Cast  Steps. — Staircases  are  also  constructed  with 
steps  cast  separately,  and  then  built  in,  in  the  same  way 
as  stone.  Illustration  No.  24  shows  various  sections 
of  steps.    Fig.  1  is  a  spandrel  step,  which  may  be  used 


412  CEMENTS  AND  CONCRETES 


for  model  dwellings,  factories,  etc.  The  tread  is  grooved 
to  afford  a  good  footing  and  prevent  dipping.  The 
dotted  line  indicates  a  square  seating  or  tail-end  of  the 
step,  which  is  embedded  in  the  wall.  Fig.  2  is  a  square 
\  step.    Fig.  3  is  a  step  with  a  moulded  and  returned 


Fig.  I.  Fig.  2.  Fig.  3.  Fig,  4. 


Sections  or  Steps. 

NO.  24. 


nosing.  F'ig.  4  is  a  similar  step,  but  having  a  moulded 
soffit.  For  cast  work  these  steps  must  have  a  square 
seating  or  tail-end,  as  indicated  by  the  dotted  lines  on 
Fig.  1,  so  as  to  bond  into  the  wall. 


NO.  25 

Treads  and  Risers, — Stairs  between  walls  are  some- 
times formed  with  treads  and  risers.  The  treads  and 
risers  are  cast  and  built  in  as  the  construction  of  the 
work  proceeds.  Sometimes  they  are  let  into  chases  and 
pinned  after  the  walls  are  built.  Illustration  No.  25 
shows  ei  section  of  treads  and  risers. 


HOW  TO  USE  THEM 


413 


Closed  Out 67^  Strings. — Staircases  are  sometimes  fin- 
ished with  a  close  outer  string,  which  prevents  dirt  or 
wet  falling  into  the  well.  Illustration  No.  26  shows 
the  section,  Fig.  1,  and  the  elevation,  Fig.  2,  of  a 
moulding  outer  string.  The  dotted  line  at  A  indicates 
a  dowel  hole  for  the  balusters.  Outer  strings,  whether 
plain  or  moulded,  are  much  stronger  when  formed  in 


Fig;  I.  Fig.  2. 

NO.  26. 


situ.  This  is  best  effected  by  fixing  a  reverse  mould 
at  each  side,  then  filling  in  the  space  from  the  top.  The 
top  is  finished  by  hand  and  the  aid  of  a  template.  The 
dowel  holes  are  formed  as  already  described. 

Concrete  Floors. — It  has  been  mentioned  that  the 
Romans,  in  the  time  of  Julius  Caesar,  were  in  the  habit 
of  constructing  their  floors  and  roofs,  as  well  as  their 
walls,  of  concrete.  According  to  an  article  in  Archaeolo- 
gia,  the  cementitious  agent  was  pozzolana.    The  lime 


414  CEMENTS  AND  CONCRETES 


was  obtained  by  burning  ' '  traverstine, ' '  The  aggregate 
usually  consisted  of  broken  tufa  for  walls,  of  broken 
lava  for  foundations  where  great  strength  was  re- 
quired, and  of  broken  pumice  where  lightness  was  es- 
sential. The  floors  were  generally  constructed  of  large 
slabs  of  concrete,  supported  on  sleeper  brick  walls. 
The  upper  surface  was  finished  with  a  layer  of  finer 
concrete  and  mosaic.  The  roofs  were  made  flat,  rest- 
ing on  brick  pillars.  The  first  known  English  patent 
fireproof  construction  was  obtained  by  one  Dekins  Bull, 
in  1633 ;  but  as  at  that  period  patentees  were  not  com- 
pelled to  disclose  what  their  patents  covered,  no  de- 
scription of  the  materials  and  methods  can  be  given. 
Up  to  the  middle  of  the  eighteenth  century  fireproof 
their  great  weight  and  cost,  were  seldom  used.  But 
towards  the  close  of  that  century  cast-iron  girders  and 
segmental  brick  arches  were  gradually  coming  into  use 
where  strength  was  essential.  Up  to  a  century  ago 
plaster  was  largely  employed  as  a  floor  material.  In 
floors  usually  consisted  of  brick  arches,  but  owing  to 
1778  Earl  Stanhope  invented  pugging  for  rendering 
wooden  floors  fireproof.  By  this  process  fillets  were 
paled  to  the  joists  at  about  one-third  of  the  height. 
Laths  were  laid  on  the  fillets  and  plastered  above  and 
below  with  a  coat  of  lime  and  chopped  hay.  The  under 
sides  of  the  joists  were  then  lathed  and  plastered  in  the 
usual  way  to  form  the  ceiling.  About  the  early  part  of 
the  last  century  wrought  iron  joists  were  substituted 
for  cast  iron  girders.  Fox  &  Barret's  floor,  designed 
about  1830,  was  the  first  in  which  an  attempt  was  made 
to  protect  the  exposed  faces  of  the  iron  joists  with  a 
fire-resisting  material.  Hornblower's  floor  is  one  of  the 
earliest  for  resisting  the  effects  of  fire»    Iron,  bricks 


HOW  TO  USE  THEM 


415 


and  plaster  are  chiefly  used  in  the  French  and  Ameri- 
can systems.  For  the  sake  of  simplicity  and  reference, 
concrete  floors  may  be  divided  into  three  kinds:  (1) 

Joist  floors/'  in  which  the  concrete  is  laid  slid  be- 
tween the  joists;  (2)  ''Tabular  floors,"  formed  with 
fireclay  tubes  or  hollow  lintels  placed  between  the 
joists  and  covered  with  concrete;  (3)  ^'Slab  floors," 
formed  in  one  piece  or  slab.  Portland, cement  concrete 
laid  in  situ  on  and  between  iron  joists  is  extensively 
used  for  fire-resisting  structures.  Cast  concrete  is  used 
for  some  parts  of  tabular  floors.  Cast  concrete  blocks 
are  used  for  the  ceiling  surface,  and  as  a  support  for 
the  rough  concrete  floor  surface.  The  blocks  are  hol- 
low, and  have  male  and  female  dovetails  on  the  sides. 
The  ceiling  surface  of  the  floors  and  the  outer  surfaces 
of  the  partitions  are  finished  with  a  thin  setting  coat  of 
gauged  putty  or  Parian.  The  chief  objects  of  fire- 
proof floors  are  to  render  each  floor  capable  of  resist- 
ing the  effects  of  fire,  so  that  fire  cannot  be  communi- 
cated from  one  floor  to  another,  and  by  making  the 
roof  fireproof,  to  prevent  the  fire  from  spreading  from 
one  compartment  to  another;  to  gain  additional 
strength,  so  as  to  avoid  as  far  as  possible  lateral  thrust 
on  the-  walls,  and  to  secure  the  building  from  attacks 
and  effects  of  both  dry  rot  and  damp.  There  have  been 
about  a  hundred  patents  for  fireproof  floors  during  the 
past  generation,  of  which  about  five  or  six  survive. 

Plaster  Floors. — Plaster  concrete,  that  is,  plaster  and 
broken  bricks,  or  similar  aggregates,  also  neat  plaster, 
were  at  one  time  used  largely  for  the  formation  of 
floors.  The  use  of  plaster  floors  was  common  in  some 
districts,  and  up  to  a  century  ago^  the  rough  plaster, 
known  as  ''floor  plaster,"  was  in  general  use  where 


416  CEMENTS  AND  CONCRETES 


gypsum  was  found  in  abundance.  Plaster  floors  were 
rarely  used  on  the  ground  level,  because  they  could  not 
resist  moisture,  which  caused  them  to  become  soft  and 
retain  the  damp.  They  were  principally  used  for  up- 
per floors.  The  gauged  plaster  was  laid  upon  reeds. 
These  reeds  were  spread  upon  the  tops  of  joists,  and 
over  them  was  laid  straw  to  keep  the  soft  plaster  from 
percolating  through  the  reeds.  The  floors  were  about 
3  inches  thick,  floated  fair,  and  finished  the  following 
day.  AVood  strips  were  placed  around  the  walls,  and 
drawn  out  when  the  plaster  began  to  set,  to  allow  for 
^he  expansion  of  the  plaster.  The  materials  being  so 
light,  the  timbers  were  less  in  size  and  number  than 
those  now  in  use.  The  joists  were  in  some  instances 
3%  inches  by  2%  inches,  fixed  wide  apart,  and  sup- 
ported  by  small  beams  about  4^/2  inches  by  3^/2  inches, 
The  undersides  between  the  joists  were  made  fair  by 
plastering  the  reeds,  but  in  the  better  class  of  work  the 
joists  were  covered  with  reeds,  and  held  in  position  with 
oak  laths,  and  plastered.  Bullock's  blood  was  used  to 
harden  the  floors  after  they  were  dry.  In  some  in- 
stances they  were  coated  with  linseed  oil  to  increase 
their  hardness.  Their  use  is  now  practically  super- 
seded by  Portland  cement  concrete. 

Joist  Concrete  Floors. — For  this  form  of  floor  the 
concrete  is  laid  between,  over  and  under  the  iron  joists 
Beyond  the  supervision  of  the  fixing  of  the  centring 
and  the  gauging  of  the  materials,  little  skilled  labor  is 
required.  The  rough  concrete  is  laid  between  and 
partly  under  the  iron  joists,  which  are  fixed  from  3  feet 
to  5  feet  apart,  according  to  the  span  and  strength  of 
the  joists.  The  centring  is  supported,  or  rather  hung, 
by  the  aid  of  timber  laid  across  the  joists  and  secured 


HOW  TO  USE  THEM 


417 


by  bolts.  The  materials  are  generally  Portland  ce- 
ment and  gravel  coke-breeze,  clinkers  and  broken 
bricks,  gauged  in  the  proportion  of  1  part  of  matrix 
to  5  of  aggregate.  Sand  equal  to  one-third  of  the 
bulk  should  be  added.  Coke-breeze  is  weak,  light  and 
elastic,  but  combustible  and  porous.  A  mixture  of 
gravel  and  breeze  in  equal  proportions  is  better  than 
either  alone.  The  proportion  of  cement  varies  accord- 
ing to  the  span  and  class  of  aggregate.  All  other 
things  being  equal,  the  strength  of  concrete  is  influ- 
enced by  the  strength  of  the  aggregate,  so  that  it 
would  take  a  greater  proportion  of  cement  to  make 
coke-breeze  concrete  equal  in  strength  to  a  concrete 
made  with  hard  aggregate,  such  as  granite,  slag  or 
brick.  The  upper  surface  of  this  class  of  floor  may 
be  finished  with  wood,  tiles  or  fine  concrete,  as  re- 
quired. Joist  concrete  floors  have  been  largely  used. 
This  is  principally  owing  to  their  supposed  cheap- 
ness, but  it  is  more  than  probable  that,  in  the  event 
of  fire,  they  would  be  dear  in  the  end,  because  the 
lower  part  of  the  flanges  are  barely  protected  from  the 
effects  of  fire,  as  the  concrete,  being  thin  at  these  parts, 
and  also  on  a  comparatively  smooth  surface,  would 
soon  crack  or  scale  off,  and  leave  the  flanges  of  the 
joists  exposed  to  the  ravages  of  fire.  They  are  also 
more  or  less  conductors  of  sound.  Caminus  concrete 
cement  is  an  excellent  material  for  the  construction 
of  fireproof  ceilings  and  partitions. 

Caminus  Concrete  Cement. — This  material  is  specially 
designed  to  produce  a  hard  and  practically  indestructi- 
ble concrete  for  the  construction  of  fireproof  floors  and 
walls.  It  is  manufactured  from  a  waste  product,  and 
all  inflammable  material,  such  as  coke-breeze,  being  en- 


418  CEMENTS  AND  CONCRETES 


tirely  dispensed  with,  the  concrete  is  thoroughly  fire- 
resisting*.  It  is  lighter  and  much  cheaper  than  Port- 
land cement  concrete,  and  is  perfectly  free  from  ex- 
pansion and  contraction  whilst  setting.  It  can  be  man- 
ufactured to  set  in  a  few  hours,  so  that  the  centres 
can  be  struck  the  day  after  the  floor  is  laid.  It  can 
be  supplied  in  a  ready  aggregated  condition,  so  that  the 
bags  may  be  hoisted  direct  to  the  floor  where  the  con- 
crete is  being  laid,  and  gauged  on  the  floor,  thus  sav- 
ing a  great  amount  of  waste,  and  also  labor  in  handling, 
mixing  and  laying. 

Concrete  Floors  and  Coffered  Ceilings. — A  method 
was  patented  by  E.  Ransom  for  decreasing  quantity  of 
material  and  yet  obtaining  equal  strength  in  floors.  The 
floor  is  divided  by  a  series  of  beams  at  right  angles 
to  each  other,  so  as  to  form  a  series  of  coffers  in  the 
ceiling.  For  instance,  for  a  floor  12  inches  thick,  the 
floor  proper  would  be  about  4  inches  thick,  and  beams 
about  3  inches  thick  and  8  inches  deep — a  rod  of  twist- 
ed iron  being  placed  in  the  centre  of  the  thickness,  and 
near  the  lower  surface  of  the  beams.  The  beams  are 
generally  about  2  feet  6  inches  from  centre  to  centre. 
The  method  of  construction  is  as  f ollov/s :  First,  form 
a  platform  or  centring;  on  this  a  series  of  core  boxes 
2  feet  3  inches  is  placed,  3  inches  apart,  so  as  to  form 
a  3-inch  beam.  The  core  boxes  must  be  tapered  and 
their  upper  edges  rounded,  so  that  they  will  draw  when 
the  centring  is  struck.  The  size  of  the  core  boxes  may 
be  altered  to  suit  the  size  and  requirements  of  the 
floor.  With  regard  to  the  iron  bars,  the  inventor  says : 
^^It  is  of  vital  importance  for  the  strength  of  the  struc- 
ture that  the  iron  bars  be  placed  no  higher  in  the  beam 
than  calculated  for;  that  the  longitudinal  centre  of 


HOW  TO  USE  THEM 


419 


these  bars  should  be  at  the  lowest  point ;  and  it  is  ad- 
visable that  the  bars  curve  upwards  slightly  and  uni- 
formly each  way  from  the  centre  to  the  ends,  so  that 
the  ends  are  from  1  to  3  inches  higher  than  the  cen- 
tres. By  preparing  the  concrete  bed  on  a  correspond- 
ing curve,  the  natural  sag  of  the  bar,  as  it  is  being 
handled  to  its  place,  gives  all  the  requisite  facility  to 
accomplish  this  purpose.  No  crooked  or  irregular 
t^visted  iron  must  be  used;  otherwise,  when  the  strain 
comes  upon  it,  it  will  perforce  straighten  and  lengthen 
out,  and  weaken  the  structure  in  so  doing.  After 
placing  the  iron,  the  rest  of  the  concrete  is  tamped  in 
place,  and  the  whole  made  to  form  a  monolithic  block. 
It  is  of  vital  importance  that  no  stop  be  made  in  the 
placing  of  concrete  from  the  time  the  beam  is  begun 
until  the  thickness  of  the  beam  is  in  place  and  a 
through  joint'  is  made.  The  web  and  the  thickness 
must  be  one  solid  piece  of  homogeneous  concrete." 

Combined  Concrete  Floors  and  Panelled  Ceilings, — A 
combined  floor  and  panelled  ceiling  may  also  be  formed 
in  concrete.  This  is  executed  as  follows :  First,  form 
a  level  platform  or  centring,  and  on  this  fix  the  re- 
verse plaster  mould,  run  and  mitred,  according  to  the 
design  of  the  ceiling.  The  intervening  panels  are  then 
made  up  with  framing,  and  the  concrete  filled  in  the 
usual  way,  and  when  set  the  centring  and  reverse 
mould  are  removed,  and  the  ceiling  cleared  off.  If  de- 
sired, a  finely  finished  and  smooth  white  surface  may 
be  obtained  by  coating  the  surface  of  the  moulds  and 
panels  with  firmly  gauged  Parian,  or  other  white  ce- 
ment, until  about  %  inch  thick,  and  when  this  is  firm 
(but  not  set),  the  rough  concrete  is  deposited  in  layers 
and  tamped  to  consolidate  the  concrete,  and  unite  it 


420  CEMENTS  AND  CONCEETES 


with  the  white  cement.  The  surface  may  also  be  fin- 
ished with  fibrous  concrete.  The  method  of  doing  this, 
also  for  carrying  out  the  above  white  cement  process,  is 
described  in    Fibrous  Concrete." 

Concrete  and  Wood. — Concrete  floors  finished  with 
flooring  boards  require  special  care  to  prevent  damp  or 
dry  rot.  There  are  various  methods  in  use  for  fixing 
and  keeping  the  flooring  boards  from  contact  with  the 
rough  concrete,  one  way  being  to  fix  wood  fillets  to  the 
joists  by  means  of  wedges  or  clamps.  Another  way 
is  to  embed  wood  fillets  or  fixing  blocks  in  the  rough 
concrete,  leaving  them  projecting  above  the  level  of  the 
iron  joists,  to  give  a  bearing  and  fixing  points  to  the 
flooring  boards;  or  fine  coke-breeze,  concrete  or  plas- 
ter screeds,  may  be  laid  at  intervals  on  the  rough 
concrete,  onto  which  the  boards  are  nailed.  Fixing 
blocks,  concrete  or  plaster  screeds,  are  preferable  to 
wood  fillets,  as  they  do  not  shrink  or  rot,  and  will 
better  resist  fire.  All  these  methods  leave  intervening 
spaces  between  the  concrete  and  the  boards,  and  unless 
thoroughly  ventilated,  they  harbor  vermin,  dirt  and 
stagnant  air.  Unless  the  wood  is  thoroughly  seasoned, 
and  the  boards  grooved  and  tongued,  dust  and  ef- 
fluvia will  find  egress  through  the  joints.  A  portion  of 
dust  and  water  when  sweeping  and  washing  the  floors 
also  finds  egress  through  the  joists;  and  as  the  concrete 
will  not  absorb  the  water,  or  allow  the  dust  to  escape, 
they  accumulate  and  become  unseen  dangers.  These 
sanitary  evils  may  be  obviated,  or  at  least  reduced  to 
a  minimum,  by  laying  the  boards  direct  on  the  con- 
crete. This  not  only,  forms  a  solid  floor  with  no  inter- 
spaces, but  admits  of  thin  boards  being  used  with  as 
much  if  not  greater  advantage  than  a  thick  board. 


HOW  TO  USE  THEM  421 


There  is  no  uneven  springing  between  the  joists,  which 
causes  friction  and  opening  of  the  joints^  and  the  whole 
thickness  is  available  for  wear.  There  is  also  less  total 
depth  of  floor,  consequently  less  height  of  building  and 
general  cost.  Another  important  advantage  of  a  solid 
floor  is  that  it  will  resist  fire  better  than  one  with  hol- 
low spaces.  It  is  here  that  the  sponginess  and  elasticity 
of  coke-breeze  concrete  as  a  top  layer  is  of  special 
service,  and  where  it  may  be  utilized  with  advantage. 
Owing  to  its  being  able  to  receive  and  retain  nails,  the 
boards  can  be  nailed  at  any  desired  place.  Wood 
blocks  for  parquet  floors  can  also  be  bedded  or  screwed 
on  the  concrete  surface.  Flooring  boards  will  lie  even 
and  solid  on  this  surface,  and  if  a  thin  layer  of  felt  or 
slag-wool  be  spread  on  the  concrete  before  the  boards 
are  laid,  a  firm  and  noiseless  floor  is  obtained.  Slag- 
wool  is  an  imperishable  non-conductor  of  heat,  cold 
and  sound,  and  it  will  not  harbor  vermin.  If  the  work 
is  in  humid  climate,  the  coke-breeze  surface  when  dry 
should  be  coated  with  a  solution  of  tar  and  pitch,  to 
prevent  atmospheric  moisture  being  absorbed  by  the 
porous  coke-breeze. 

Concrete  Drying. — To  prevent  dry  rot  It  is  of  the  ut- 
most importance  that  the  concrete  should  be  thoroughly 
free  from  moisture  before  the  flooring  boards  are  laid 
and  fixed.  The  drying  of  concrete  is  a  question  of 
time,  which  depends  upon  the  amount  of  water  used 
for  gauging,  the  thickness  and  the  temperature.  It 
may  take  from  three  days  to  three  weeks  or  even  three 
months.  The  drying  can  be  accelerated  by  directing 
currents  of  hot  air  on  the  lower  surface,  or  by  laying 
some  absorbent  material,  such  as  dry  sawdust  or  brick 
dust,  on  the  upper  surface,    As  soon  as  the  surface 


422  CEMENTS  AND  CONCRETES 


moisture  is  absorbed,  or  the  dry  material  has  no  further 
absorbent  power,  it  should  be  removed  to  allow  the 
mass  to  be  air  dried.  Another  way  is  to  lay  the  floor 
in  two  coats,  and  to  allow  one  coat  to  dry  before  the 
other  is  laid.  For  instance,  if  the  floor  is  to  be  6 
inches  thick^  the  first  coat  is  laid  with  rough,  but 
strong*  concrete,  the  aggregate  being  the  best  available ; 
but  taking  gravel  and  coke-breeze  to  be  the  most 
plentiful,  it  will  be  best  to  assimilate  and  combine  the 
good  qualities  of  each  to  equalize  their  defects  by  mix- 
ing them  in  equal  proportions.  If  brick  is  plentiful, 
and  broken  to  properly  graduated  sizes,  it  will  give 
better  results  than  gravel  or  breeze.  The  mixed  ag- 
gregate is  gauged  5  parts  to  1  of  cement,  and  laid  4^/2 
inches  thick,  and  gently  but  firmly  beaten  in  situ,  the 
surface  being  left  rough  to  give  a  key  for  the  second 
coat.  The  second  coat  is  not  laid  until  the  first  is 
dry,  and  consists  of  one  part  cement  to  5  of  sifted  and 
damped  coke-breeze,  gauged  stiff,  and  laid  1%  inches 
thick,  beaten  in  situ,  ruled  level,  and  any  ridges  being 
laid  fair  with  a  long  hand-float.  The  moisture  of  the 
second  coat,  by  reason  of  the  density  of  the  first  coat, 
will  only  be  absorbed  to  a  small  degree,  while  the 
greater  portion  will  be  taken  up  by  the  atmosphere, 
and  enable  the  combined  coats  to  dry  sooner  than  if 
laid  in  one.  The  first  coat  should  be  laid  as  soon 
as  the  roof  is  on,  so  as  to  give  all  possible  time  for  it 
to  dry^  and  the  second  coat  to  be  laid  and  dried  before 
the  flooring  is  laid.  When  coke-breeze  is  not  avail- 
able for  the  second  coat,  use  soft  brick,  broken  to  pass 
through  a  3-16-inch  sieve.  The  method  of  laying  floors 
in  two  coats  is  only  given  as  an  alternative  plan,  and 
as  an  example  of  a  process  used  in  some  parts.  Greater 


HOW  TO  USE  THEM 


423 


strength,  as  a  whole,  and  more  perfect  cohesion  be- 
tween the  two  coats,  is  obtained  by  laying  the  second 
coat  as  soon  as  the  first  is  laid,  or  at  least  while  it  is 
green. 

Concrete  Slab  Floors. — The  term,  slab  floor,  is  applied 
to  a  concrete  floor  form.ed  in  situ,  and  in  one  piece  or 
slab.  It  must  not  be  confounded  with  slab  pavements, 
which  are  constructed  with  a  number  of  small  cast 
slabs.  Slab  floors  are  usually  made  without  exterior 
iron  supports,  but  in  a  few  instances  iron  T  pieces  or 
bars  have  been  used  as  internal  supports.  Bearing  in 
mind  the  lasting  properties  of  the  old  Roman  slab 
floors,  and  the  enormous  strength  of  the  modern  exam- 
ples at  home,  which  are  unsupported  by  iron,  and  are 
practically  indestructible,  it  seems  strange  that  they  are 
not  in  more  general  use,  and  that  for  some  inexplica- 
ble reason  preference  is  given  to  shrinking,  rotting 
and  combustible  floors^  composed  of  poor  iron  and  tim- 
ber instead  of  the  best  work  and  material,  which,  if  a  lit- 
tle deai^er  at  first,  is  infinitely  superior  and  vastly 
cheaper  in  the  long  run.  The  great  sanitary  advan- 
tages and  fire  and  damp  resisting  powers  of  concrete 
slab  floors  are  the  highest  known.  The  construction  of 
slab  floors  is  simple,  and  similar  in  many  respects  to 
that  already  described  for  stair  landings  and  ordinary 
concrete  and  joist  floors.  There  are  several  methods 
of  supporting  the  floors,  the  first  and  most  common 
being  to  leave  a  sand  course  or  to  cut  a  horizontal  chase 
in  the  walls  to  receive  the  ends  of  the  floors.  The 
second  is  to  lay  the  floors  when  the  walls  are  floor 
high,  and  build  the  higher  walls  on  it  when  set.  This 
method,  while  making  sound  work,  is  not  always  prac- 
ticable or  convenient,  owing  to  the  delay  in  building 


424  CEMENTS  AND  CONCRETES 


while  waiting  for  the  floors  to  set.  The  third  method 
is  to  build  corbelled  ledges  in  the  walls,  so  as  to  carry 
the  floors.  The  centring  for  slab  floors  should  be  per- 
fecth^  rigid,  water-tight  and  slightly  cambered  towards 
the  ceiling  centre.  This  camber  gives  more  strength 
to  the  floor,  and  lessens  liability  to  crack  when  remov- 
ing the  centring.  If  joists  are  not  used,  the  centring 
is  supported  on  Avall  boards  and  centre  struts.  An- 
other way  which  gives  great  additional  strength  is  to 
form  the  centring  level,  but  having  all  the  edges  at  the 
wall  rounded  off,  so  as  to  form  the  floor  like  an  in- 
verted sink  or  tray.  The  horizontal  chases  in  this  case 
should  be  made  wider  than  the  thickness  of  the  floor  to 
allow  for  a  thickness  of  rim.  The  extra  width  of  chase, 
which  may  be  one  or  two  bricks  thick,  according  to  the 
width  of  span,  is  made  below  the  centring  or  line  of 
ceiling,  the  angles  being  coved  by  rounding  the  edges 
of  centring.  The  coved  rim  gives  greater  strength 
with  a  less  thickness  of  floor.  The  cove  may  be  left 
plain  or  used  for  a  cove  for  a  plaster  cornice,  or  rough- 
ened and  used  as  a  bracket  for  the  same  purpose.  The 
expansion  of  concrete  floors  having  large  areas,  or 
where  hot  cement  has  been  used,  has  been  known  to 
disturb  the  walls^  causing  cracks  and  displacement  of 
brick  and  stone  work.  This  may  be  prevented  by 
isolating  the  floor  ends  from  the  walls.  This  is  done 
by  forming  expansion  partitions  or  linings  in  the  chases, 
the  linings  being  composed  of  slag,  felt  or  wood  shav- 
ings, straw,  reeds  or  other  compressible  material.  The 
chase  should  be  sufficiently  deep  to  allow  for  a  com- 
pressible lining  about  IV2  inches  thick,  and  a  fair  bed 
for  the  slab  floor.  Care  must  be  taken  to  leave  a  few 
half  bricks  solid  at  intervals,  say  from  3  to  4  feet 


HOW  TO  USE  THEM 


425 


apart,  to  support  the  upper  walls  until  the  floor  is  set. 
Compressible  linings  may  be  used  for  floors  supported 
on  corbelled  ledges;  and  when  the  expansion,  and  in 
many  cases  subsequent  contraction,  has  finally  finished, 
the  linings  can  be  taken  out,  and  the  vacant  space 
filled  up  with  fine  concrete,  or  utilized  as  a  ground  key 
for  cement  skirtings.  If  girder  or  iron  posts  are  iso- 
lated from  the  walls  by  means  of  compressible  linings, 
the  eff^ects  of  expansion  and  sound  are  limited.  In 
some  instances  a  judicious  use  of  iron  may  be  made. 
For  instance,  large  areas  may  be  divided  with  three  or 
four  rolled  iron  joists,  so  as  to  form  shorter  spans  or 
smaller  bays.  Joists  tend  to  bind  the  walls  together, 
and  to  serve  as  scaffold  bearings  for  building  the  upper 
parts  of  walls.  They  may  also  be  used  for  hanging 
the  centring  on  instead  of  strutting,  or  as  aids  to  ihe 
strutting.  Joists  may  also  be  used  as  integral  sup- 
ports at  unsupported  ends  of  concrete  floors.  They 
should  be  so  fixed  that  the  lower  flanges  are  not  less 
than  1  inch  above  the  lower  surface  of  the  concrete. 
The  whole  strength  of  iron  is  brought  more  fully  into 
use  by  fixing  it  near  the  lower  surface.  If  fixed  near 
the  centre,  or  at  the  axis  of  neutral  stress,  a  correspond- 
ing part  of  the  strength  is  comparatively  of  little 
value„ 

Construction  of  Slab  Floors. — Portland  cement  as  a 
matrix  is  indispensable.  The  unequal  nature  of  gravel 
and  col^e-breeze  renders  them  unfit  and  unsafe  aggre- 
gates for  this  class  of  work.  Broken  brick  being  cheap, 
and  obtainable  in  most  districts,  affords  a  ready  aggre- 
gate, and  may  be  used  with  safety  and  success.  In 
ordinary  cases  of  concrete  construction,  the  whole 
thickness  is  usually  made  with  one  rate  of  gauge ;  but 


426  CEMENTS  AND  CONCRETES 


for  slab  floors  covering  large  areas,  and  unsupported 
by  iron  or  other  supports,  exceptional  strength  is  re- 
quired. Stronger  results  are  obtained  by  making  up 
the  whole  thickness  with  different  rates  of  gauge.  Tak- 
ing the  usual  gauge  for  floors  as  from  4  to  5  parts  of 
aggregate  to  one  of  cement,  and  used  for  the  whole 
thickness,  it  gives  an  unequal  strength,  a  part  of  which 
is  comparatively  of  little  use,  especially  at  the  neutral 
axis;  but  if  the  cement  is  divided  so  as  to  form  an 
ordinary  coat  in  the  centre,  and  stronger  coats  at  the 
upper  and  lower  surfaces  at  the  points  of  greatest 
strain,  the  upper  being  compressive  and  the  lower  ten- 
sive, a  better  and  more  accurate  arrangement  of 
strength  and  allowance  for  disposition  of  strains  is  ob- 
tained. The  additional  strength  at  the  proper  places 
is  obtained  not  only  by  the  use  of  additional  cement, 
but  by  the  method  of  construction,  which  enables  the 
same  quantity  of  cement  as  gauged  for  the  usual  rate 
for  forming  the  whole  thickness  in  one  coat  to 
be  used  more  profitably.  Take  the  section  of 
an  iron  joist  as  an  example;  this  gives  divided 
yet  united  strength,  which  sounds  paradoxical, 
but  is  true.  The  flanges  sustain  the  greatest 
strains,  and  the  web  comparatively  little.  With  con- 
crete, the  strong  coats  at  the  upper  and  lower  surfaces 
represent  the  flanges,  and  the  ordinary  coat  the  web. 
As  already  stated,  the  increased  and  profitable  dis- 
tribution of  strength  is  obtained  by  the  method  of  con- 
struction. For  instance,  take  a  slab  floor  20  feet  by 
14  feet  and  12  inches  thick,  without  iron  joists  or  other 
supports,  and  intended  to  carry  a  safe  load  of  2V2  cwt. 
per  superficial  foot,  in  addition  to  its  own  weight  of  say 
1  cwt.  per  square  foot.   This  floor  is  laid  in  three  coats, 


HOW  TO  USE  THEM 


427 


the  first  composed  of  1  part  cement  and  2  of  fine  broken 
bricks  gauged  stiff,  and  laid  2  inches  thick ;  the  second 
composed  of  1  part  cement  and  6  of  coarse  broken 
bricks  gauged  stiff  and  laid  and  rammed  8  inches  thick ; 
and  the  third  composed  of  1  part  cement  and  2  of  fine 
broken  bricks  gauged  stiff  and  laid  2  inches  thick. 
If  the  upper  surface  is  intended  for  hard  frictional  wear 
a  slight  difference  is  made  in  the  gauge  and  materials. 
The  first  coat  is  composed  of  2  parts  of  cement  and  5  of 
fine  broken  bricks  gauged  stiff  and  laid  2  inches  thick ; 
the  second  of  1  part  cement  and  6  of  coarse  broken 
bricks  gauged  stiff  and  laid  and  rammed  till  8  inches 
thick ;  and  the  third  coat  composed  of  1  part  cement  and 
2  of  fine  crushed  slag  or  granite.  It  will  be  seen  that 
this  constructive  method  gives  the  desired  positions  of 
strength^  and  the  total  quantity  of  cement  in  the  united 
gauges  is  1  part  to  4,  and  up  to  5  parts  of  aggregate. 
The  fine  broken  bricks  should  be  passed  through  a  1/2- 
inch  sieve,  and  the  coarse  through  a  2-inch  screen, 
taking  care  that  the  latter  contains  a  greater  quantity 
of  the  smaller  pieces  than  of  the  larger.  It  must  be 
clearly  understood  that  the  second  coat  must  be  laid 
before  the  first  is  set ;  also  that  the  third  is  laid  before 
the  second  is  set,  so  as  to  ensure  perfect  cohesion  be- 
tween each  coat,  and  the  absolute  homogeneity  of  the 
whole  mass. 

Hollow  Floors. — Greater  lightness  in  concrete  floors  is 
obtained  by  the  use  of  concrete  tubes.  If  the  tubes  are 
placed  apart  and  in  the  centre  of  the  floor  thickness, 
a  hollow  homogeneous  concrete  slab  is  formed.  The 
vertical  divisions  between  the  tubes  connect  the  upper 
and  lower  coats^  as  with  a  web  of  a  joist  connecting  the 
upper  and  lower  flanges.    The  method  of  construction 


428  CEMENTS  AND  CONCRETES 


is  simple  and  expeditious.  For  example,  for  a  slab 
floor  10  inches  thick,  first  lay  a  coat  2  inches  thick  of 
the  stronger  and  finer  concrete,  as  described  for  the 
12-inch  slab  floor,  and  when  this  is  firm  lay  5  or  6- 
inch  tubes  from  wall  to  wall.  Bed  the  sides  with  rough 
concrete,  and  lay  another  row  of  tubes  parallel  with  the 
first  row  and  about  2  inches  apart,  and  so  on  until  the 
floor  area  is  covered;  then  make  up  interspaces  with 
rough  concrete  till  level  with  the  upper  surfaces  of  the 
tubes,  and  then  cover  this  with  a  coat  of  fine  concrete  2 
inches  thick.  Concrete  tubes  or  common  earthenware 
drain  pipes  may  be  used.  Half-circle  pipes,  laid  on 
their  side  edges,  may  be  used  to  save  concrete  and 
weight  in  joist  floors,  etc. 

Concrete  Roofs. — Concrete  roofs  require  special  care 
to  render  them  watertight.  Subsidence  in  the  brick 
work  of  new  buildings  is  often  the  cause  of  cracks  on 
concrete  roofs.  The  roof  should  have  a  good  camber, 
to  give  greater  strength  and  allow  for  the  fall  of  wa- 
ter to  the  outer  edges.  The  rough  coat  should  be  laid 
and  well  consolidated  by  ramming  or  beating,  and  then 
left  for  seven  days  (the  longer  the  better)  before  the 
topping  is  added.  The  upper  coat  should  be  strongly 
gauged  with  fine  aggregate,  as  in  Eureka."  If  possi- 
ble, the  topping  should  be  laid  in  one  piece.  If  the 
area  is  too  large  to  be  laid  and  finished  in  one  piece, 
the  joints  of  the  bays  should  overlap.  This  is  done 
by  rebating  the  screed  rules,  so  as  to  allow  one-half  of 
topping  thickness  to  go  under  a  part  of  the  rule  and 
form  an  underlap  or  ledge  about  I/2  inch  wide,  and 
when  the  adjoining  bay  is  laid  an  overlapped  but  level 
joint  is  the  result.  Eoofs  exposed  to  the  sun's  heat 
should  be  kept  damp  for  several  days  after  being  laid, 


HOW  TO  USE  THEM 


429 


as  joints  are  affected  by  the  heat  as  well  as  by  deflec- 
tion of  centring  or  subsidence  of  walls.  Compressible 
linings  or  wood  strips  should  be  used  round  the  walls 
to  counteract  any  expansion.  All  concrete  roofs  should 
have  a  cement  skirting  6  inches  high  and  1  inch  thick 
well  keyed  into  the  walls.  If  linings  are  not  used  when 
the  topping  is  laid,  the  topping  should  be  turned  up  on 
the  walls,  so  as  to  form  a  rim,  to  prevent  water  get- 
ting between  the  roof  and  the  walls.  Greater  heat  and 
damp-resisting  powers  are  obtained  by  laying  the  up- 
per surface  with  ^^-inch  thick  coat  of  special  concrete, 
composed  of  1  part  of  Portland  cement,  I/2  part  of 
slaked  lime  and  1  part  of  firebrick  dust.  This  should 
be  consolidated  with  a  hand-float,  and  finished  fine  and 
close  with  a  trowel. 

Notes  on  Concrete, — When  calculating  the  strength  of 
floors,  stairs,  etc.,  the  following  facts  should  be  borne 
in  mind:  Portland  cement,  when  new,  is  too  hot;  sets 
more  rapidly  and  expands  more  than  old  cement.  The 
finest  ground  cement  is  the  best  and  strongest.  The 
time  in  setting,  and  in  which  the  maximum  strength  is 
attained,  varies  according  to  the  age  of  the  cement,  the 
quantity  of  water  used,  and  the  mode  of  gauging  and 
the  mean  atmospheric  temperature.  The  maximum 
strength  of  a  briquette  of  mature  cement  is  maintained, 
while  one  of  new  cement  ^^goes  back."  A  briquette  of 
matured  cement  will  stand  a  tension  strain  of  550 
pounds  per  square  inch,  and  a  crushing  weight  of  6,000 
pounds  per  square  inch.  A  briquette  of  neat  cement  is 
more  brittle  than  one  of  concrete.  Briquettes  mature 
more  rapidly  than  thick  slab  floors.  The  adhesive 
strength  of  Portland  cement  is  about  85  pounds  per 
square  inch.    The  adhesive  strength  increases  more 


430 


CEMENTS  AND  CONCEETES 


rapidly  than  the  cohesive.  A  mass  with  a  surface 
large  in  proportion  to  its  volume  sets  more  rapidly  than 
a  mass  with  a  small  area  in  proportion  to  its  volume. 
Masses  subject  to  pressure  set  more  rapidly  and  attain 
greater  hardness  than  masses  not  so  pressed.  The 
average  compressive  strength  of  concrete  is  about  eight 
times  its  tension  strength.  The  proportion  of  com- 
pressional  and  tensional  strength  varies  according  to 
the  quality  and  quantity  of  the  aggregate.  The  strength 
of  concrete  depends  greatly  on  the  proportion  of  the 
matrix  and  aggregate ;  also  on  the  strength  of  the  lat- 
ter. As  regards  bricks,  it  must  be  remembered  that 
there  is  a  wide  difference  between  the  tensile  strength 
of  hard,  well-burnt  bricks  and  soft  stocks.  No  bricks 
are  so  strong  as  cement,  the  best  kinds  being  about 
one-fourth  the  strength  of  neat  cement.  Taking  the 
gauge  as  one  part  of  cement  to  4  of  broken  brick,  the 
strength  of  the  concrete  will  be  about  tv/o-fifths  of  neat 
cement,  but  for  safe  and  practical  calculations  it  will 
be  best  to  take  the  strength  as  one-fourth  of  neat  ce- 
ment. Square  slabs  are  stronger  than  rectangular 
slabs.  Slab  floors  being  homogeneous  throughout,  the 
whole  weight  is  a  dead  weight,  and  consequently  there 
is  no  thrust  on  the  walls.  With  regard  to  the  live  load 
or  weight  which  fl.oors  should  be  constructed  to  carry, 
some  difference  of  opinion  exists.  Hurst  sa^^s  that  for 
dwellings  l^y4  cwt,  public  buildings  %  cwt.  and  ware- 
houses and  factories  2^/^  cwt.  are  safe  calculations. 
Others  assert  that  for  domestic  buildings  1  cwt.  per  foot 
would  be  ample  for  all  contingencies.  An  American 
authority  states  40  lbs.  is  sufficient  for  ordinary  pur- 
poses.   The  following  table  shows  the  results  of  tests 


HOW  TO  USE  THEM 


431 


of  slab  floors  made  without  iron.  The  slabs  were  sup- 
ported all  round,  and  uniformly  loaded  with  bricks. 


Test  of  Slab  Floors. 


No. 

Length 
between 
Sup- 
ports, 
feet. 

Breadth 
between 
Sup- 
ports, 
feet. 

Thick- 
ness, 
feet. 

Age  in 
Days. 

Breaking 
Weight,  in 
cwt.  per 
sq.  ft. 

Weight  of 
Slab,  in 
cwt.  per 
sq.  ft. 

Total 
Breaking 
Weight,  in 
cwt.  per 
sq.  ft. 

1 

14.5 

6.75 

.5 

7 

3. 

.54 

3.54 

2 

14 

2.76 

3.30 

3 

(< 

21 

8.88 

9.42 

4 

13.5 

7 

1.07 

1.61 

5 

6.75 

14 

2.51 

3.05 

6 

21 

2.84 

3.38 

Cast  Concrete. — Innumerable  patents  have  been  ob- 
tained for  a  combination  of  materials,  also  moulds  for 
the  construction  of  artificial  stone.  Among  the  many 
that  may  be  mentioned  is  Mr.  Ranger's  system.  He  ^ 
obtained  a  patent  in  1832  for  artificial  stone  formed 
with  a  lime  concrete.  The  aggregate  consisted  of 
shingle,  broken  flints,  mason's  chippings,  &c.  The  in- 
ventor stated  that  the  best  results  were  obtained  by 
using  30  lbs.  of  an  aggregate  of  a  siliceous  or  other 
hard  nature,  3  lbs.  powdered  lime,  and  18  ozs.  boiling 
water.  No  more  of  *the  materials  were  gauged  at  the 
time  than  were  sufficient  to  fill  one  mould,  as  the  boil- 
ing water  caused  the  concrete  to  set  very  rapidly.  This 
material,  after  fifty  years'  exposure  is  still  sound  and 
shows  no  sign  of  decay.  No  artificial  stone  equals,  far 
less  excels,  the  strength  and  durability,  sharpness,  and 
evenness  of  Portland  cement  concrete.  This  form  of 
artificial  stone  is  now  extensively  used  as  a  substitute 


432  CEMENTS  AND  CONCRETES 


for  natural  stone,  for  window  heads,  string  courses, 
sills,  columns,  copings,  keystones,  and  many  other  archi- 
tectural, constructive,  and  decorative  features.  Fig- 
ures, animals,  bas-reliefs,  capitals,  panels,  can  be  made 
in  fine  concrete  with  all  the  relief,  undercut,  and  fine 
detail  which  distinguishes  high-class  from  inferior 
work.  Cast  work  has  the  advantage  over  in  situ  work 
that  any  defect  can  be  detected  previous  to  fixing.  The 
methods  of  moulding  and  casting  various  works  are 
given  in  the  following  pages. 

Concrete  Dressings, — Architectural  works,  especially 
large  or  plain  parts,  are  generally  cast  in  wood  moulds. 
If  there  are  ornamental  parts  in  the  blocks,  a  combina- 
tion of  wood  and  plaster,  and  sometimes  gelatine,  is 
used  for  the  moulds ;  wood  for  the  main  or  plain  parts, 
plaster  for  circular  or  moulded  parts,  and  gelatine  for 
undercut  parts.  The  plaster  or  gelatine,  as  the  case 
may  be,  is  screwed  on  or  let  into  rebated  parts  of  the 
wood.  Ornamental  parts  are  sometimes  cast  separately, 
and  then  fixed  on  the  main  cast.  They  may  also  be 
cast  separately  and  laid  into  the  main  mould  (face 
inwards),  and  the  whole  is  cast  together  in  a  somewhat 
similar  way  to  that  described  for  '^bedded  enrich- 
ments'' in  fibrous  plaster  cornices. 

Considerable  skill  and  ingenuity  has  been  displayed 
in  the  construction  of  wood  moulds  for  casting  concrete 
blocks  for  architectural  purposes.  Many  methods  have 
been  emploj^ed  for  fixing  the  sides  and  ends  together, 
and  also  to  the  bottom  of  the  mould,  leaving  one  or 
more  parts  unfixed  to  facilitate  the  release  of  the  cast. 
The  primitive  method  is  to  fix  the  various  parts  of  the 
mould  with  screws.  This  is  a  slow  and  unreliable 
process,  as  the  continual  screwing  and  unscrewing  for 


HOW  TO  USE  THEM 


433 


each  cast  soon  wears  the  screw-holes,  and  the  sides  be- 
come loose  and  out  of  square,  causing  the  casts  to  get 
out  of  their  true  form.  Hinges,  also  hooks  and  eyes, 
have  been  used  for  the  same  purpose,  but  they  are 
liable  to  the  same  defects  as  the  screws  when  subject 
to  long  use. 


—Wedge  Mould  for  Casting  Blocks,  Mouldes 
Lintels,  Sec, 

NO.  27. 


Thumbscrews  to  fit  into  iron  sockets  are  also  used, 
but  they  are  too  expensive  for  ordinary  work,  and  are 
unsuitable  for  small  moulds.  One  of  the  most  simple 
and  reliable  methods  is  the  ^Svedge  mould,"  invented 
by  an  architect.  It  is  easily  made,  and  expeditious  in 
working.  Even  after  long  and  constant  use,  the  casts 
are  alwa^^s  accurate  in  form  and  size.  The  wedges  and 
the  rebated  ends  allow  the  various  parts  to  be  correct- 
ly fixed  and  held  in  position.  Illustration  No.  27  shows 
the  method  of  construction.    The  various  parts  are 


434 


CEMENTS  AND  CONCRETES 


named,  and  the  sketch  is  self-explanatory.  When  the 
moulds  are  extra  deep,  it  is  necessary  to  make  two  or 
more  sets  of  tenons  and  wedges  at  each  angle.  When 
there  are  a  large  number  of  casts  required  the  mould 
ends  are  strengthened  by  binding  the  projecting  ends 
with  hoop  iron.  This  method  has  been  adopted  for 
casting  a  lot  of  blocks.  Illustration  No.  28  shows  two 
useful  kinds  of  moulds.  Fig.  1  is  a  simple  form  of 
mould  adapted  for  plain  blocks,  caps,  lintels,  &c.  A,  A, 
are  the  sides,  which  are  grooved  into  the  ends  B,  B,  and 


F^ig.  I.  Fig.  2. 


NO.  28. 


held  together  by  the  bolts  and  nuts,  C,  C,  two  on  each 
side.  The  bolts  may  be  about  %  inch  diameter,  with 
a  good-sized  square-head  at  one  end,  and  a  washer  and 
nut  at  the  other.  This^  having  no  bottom,  is  termed  a 
bolted  frame  mould.  It  should  be  laid  on  a  bench  or 
moulding  board  before  the  cast  is  filled  in.  Fig.  2  is 
a  section  of  a  combined  wood  and  plaster  mould  on  the 
wedge  principle,  adapted  for  casting  a  strong  course 
moulding.  A  is  a  moulding  board,  II/2  inches  thick, 
formed  with  two  or  more  boards;  a  is  one  of  two  or 
more  cross  ledges,  1  inch  thick,  on  which  A,  the  ground, 
is  nailed,    B  is  a  width  board,  1  inch  thick,  which  is 


HOW  TO  USE  THEM 


435 


nailed  on  to  A.  This  gives  a  point  of  resistance  to  the 
plaster  piece  G  and  the  side  board  G.  D  is  a  side  board 
on  which  E  is  screwed.  E  forms  the  sloping  part  of 
the  weathering.  F  is  one  of  two  or  more  vertical 
wedges  which  hold  D  E  in  position.  The  sockets  for 
the  wedges  F  are  made  between  the  cross  ledges,  so 
that  the  wedge  will  project  below  the  ground  A.  This 
allows  the  wedges  to  be  more  easily  driven  out  when 
the  cast  is  set.  G  is  the  back  or  plain  side  board.  H 
is  a  fillet,  1%  inches  square,  screwed  on  to  the  ground 
A.  I  and  J  are  two  folding  wedges,  or,  in  other  words, 
wedges  driven  in  opposite  directions.  These  hold  G 
in  position.  Two  or  more  of  these  folding  wedges  are 
required,  according  to  the  length  of  the  mould.  The 
same  remarks  apply  to  the  vertical  wedges  F.  The  lat- 
ter form  of  wedge  is  only  giA^en  as  an  alternative.  The 
end  pieces  are  held  in  position  by  dropping  them  into 
grooves  in  a  similar  way  as  shown  in  the  previous  fig- 
ure, with  the  exception  that  the  grooves  are  cut  in  the 
sides  instead  of  the  ends.  K  is  a  gauge  rule  which  is 
used  for  ruling  the  upper  surface  of  the  cast  fair.  This 
may  also  be  done  by  working  a  straight-edge  longi- 
tudinally. The  dotted  line  at  L,  the  concrete,  indicates 
the  wall  line.  The  level  part  of  the  weathering  up  to 
this  line,  or  if  splayed  from  the  outer  member  of  this 
line,  must  be  finished  smooth  to  allow  the  water  to  run 
freely  off.  When  the  cast  is  set,  the  wedges  are  with- 
drawn, and  the  sides  and  ends  released.  The  cast  is 
then  turned  over  on  its  back  end  or  top  side  on  a  board, 
and  then  the  plaster  piece  and  the  wood  ground  is  taken 
off.  If  the  cast  is  green,  it  should  be  turned  over  on 
old  sacks  or  wet  sawdust,  so  as  to  protect  the  arrises, 
and  avoid  fractures. 


436  CEMENTS  AND  CONCRETES 


Illustration  No.  29  shows  a  method  commonly 
adopted  for  constructing  moulds  for  sills  and  copings. 
Fig.  1  is  the  section  of  a  mould  for  a  window  sill.  A 
is  the  moulding  board,  made  with  two  or  more  pieces, 
each  114  inches  thick;  a  is  one  of  two  or  more  cross 
ledges,  made  with  1  inch  stuff,  on  which  A  is  nailed.  B 
is  the  width  board,  made  of  %  inch  stuff,  nailed  on  to 
A.  C  is  a  block,  1%  inches  thick,  which  is  nailed  on 
to  B.  These  blocks  are  placed  about  a  foot  apart,  or 
so  that  they  will  carry  the  lining  D,  1  inch  thick.  A 


Fig:  I.  Fig.  2. 


Fig.  I.— Section  of  Mouli>  for  Casting  Sills. 
Fig.  2.— Section  of  Mouli)_^for  Casting  Coping. 

NO.  29. 

groove  or  an  iron  tongue  E  is  made  in  B,  and  a  piece 
of  thick  hoop  iron  or  iron  bar  is  placed  loosely  in  the 
groove  before  the  cast  is  filled  in.  F  is  a  fixed  side, 
11/4  inches  thick.  G  is  a  fillet,  inches  square,  nailed 
on  to  F,  and  screwed  on  to  moulding  board  A.  H  is  a 
loose  side,  I14  inches  thick,  on  which  the  fillet  I  is 
nailed.  J  is  one  of  two  or  more  clips,  which  turn  on 
a  screw,  and  are  used  to  hold  the  loose  side  H  in  posi- 
tion. These  clips  are  made  and  used  in  the  same  way 
as  described  for  fibrous  slabs.  As  compared  with 
wedges,  clips  are  always  in  position  ready  for  use,  are 


HOW  TO  USE  THEM 


437 


not  liable  to  be  mislaid,  and  when  the  fillets  are  fixed 
on  to  the  side  pieces,  the  clips  keep  the  sides  frona 
rising  as  well  as  expanding.  K  is  a  throating  or  water 
groove,  which  is  formed  in  the  concrete  L,  with  a  rule 
having  a  rounded  edge.  Two  blocks,  dished  at  the 
inner  ends,  must  be  fixed  one  at  each  end  of  the  mould, 
so  as  to  form  a  stool  or  bed  for  the  superstructure.  The 
position  and  form  of  the  groove  is  obtained  from  sink- 
ings cut  in  the  end  pieces  of  the  mould.  The  end  pieces 
are  held  in  position  by  grooves  cut  in  the  side  pieces 
in  a  similar  way,  as  already  described,  with  the  excep- 
tion that  the  grooves  are  cut  in  the  side  pieces,  instead 
of  the  end  pieces.  AA^hen  setting  out  the  mould,  an 
extra  length  must  be  allowed  for  the  side  pieces  for  the 
grooves.  A  part  of  the  upper  surface  of  the  cast  (be- 
ing the  part  which  projects  beyond  the  line  of  wall) 
must  be  finished  fair  by  hand  at  the  same  time  as  form- 
ing the  water  groove.  This  must  be  done  while  the  cast 
is  green.  When  the  cast  is  released  from  the  mould, 
the  iron  tongue  will  be  found  firmly  embedded  in  the 
concrete.  Fig.  2  is  a  section  of  a  wood  mould  adapted 
for  casting  wall  copings.  A  is  the  ground  of  a  mould- 
ing board,  which  may  be  made  of  l^/i-inch  stuff,  and  in 
2  or  more  widths ;  a  is  one  of  two  or  more  cross  ledges, 
1  inch  thick,  on  which  A  is  fixed.  B,  B,  are  blocks 
about  114  inches  thick,  placed  about  1  foot  apart.  C, 
C,  are  linings,  1  inch  thick,  nailed  to  B,  B.  D  is  a 
fixed  side,  I14  inches  thick.  E  is  a  fillet,  II/2  inches 
square,  fixed  to  D,  and  then  screwed  on  to  A.  F  is  a 
loose  side,  1^/4  inches  thick,  on  which  is  nailed  the  fillet 
G,  11/2  inches  square.  This  strengthens  the  sides  and 
affords  the  fixing  point  for  the  clip  H.  The  water 
grooves  I,  I,  and  the  hollowed  part  in  the  middle  of  the 


438  CEMENTS  AND  CONCRETES 


concrete  J  (made  to  save  materials  in  weight)  are 
worked  from  the  end  pieces  of  the  mould,  which  are  let 
into  the  grooves^  as  described  in  the  previous  diagram. 
If  the  moulds  are  deep,  wood  or  iron  clamps  may  be 
fixed  across  the  sides  to  keep  them  in  position,  as  shown 
by  K.  The  moulding  boards  in  this  and  the  previous 
figures,  if  strongly  made,  can  be  used  for  a  variety  of 
similar  purposes.  When  introducing  cast  instead  of 
run  moulded  work,  I  used  iron  and  zinc  plates  to 
strengthen  and  make  more  durable  plain  surfaces  on 
wood  moulds ;  but  owing  to  the  expense  and  trouble  in 
fixing  the  plates  to  the  woodwork,  they  were  aban- 
doned, and  by  using  a  better  class  of  wood,  and  in- 
durating the  surface  of  the  mould  with  hot  paraffin 
wax,  sharp  and  clean  casts  were  more  cheaply  pro- 
duced. Cast-iron  moulds  may  be  used  where  there  is 
a  large  number  of  casts  required.  They  may  also  be 
advantageously  used  for  stock  designs,  such  as  plain 
moulded  balusters.  Wood  moulds  are  rendered  more 
durable  and  impervious  to  wet  by  brushing  them  with 
hot  paraffin  wax,  and  then  forcing  it  into  the  wood  by 
ironing  with  a  hot  iron.  The  use  of  paraffin  wax  and 
oil  has  already  been  described. 

Mouldings  Cast  '^In  Situ/^ — Casting  cornices,  cop- 
ings, &c.,  in  situ  is  now  frequently  employed  for  con- 
crete. The  advantages  of  this  system  over  shop  cast 
work,  are,  that  the  work  is  readily  done,  and  the  cart- 
age or  moving  from  the  workshops  to  the  building,  and 
the  fixing,  are  dispensed  with. 

Illustration  No.  30  shows  the  method  of  constructing 
and  fixing  various  kinds  of  casting  moulds  for  in  situ 
work. 

Fig.  ]  shows  the  section  of  a  cornice,  casting  mould, 


440  CEMENTS  AND  CONCRETES 


and  supporting  bracket.  Wood  moulds  are  generally 
used  for  small  or  plain  mouldings,  but  where  the  profile 
is  undercut  or  of  an  intricate  nature,  a  plaster  mould 
is  preferable,  as  it  is  easier  and  cheaper  to  construct  a 
plaster  mould  than  cut  the  irons  which  are  necessary 
for  a  wood  mould  for  a  special  design.  Fibrous  plaster 
moulds  may  be  used  for  this  class  of  work,  but  to  illus- 
trate another  method  a  combined .  wood  and  plaster 
mould  is  given.  M  is  a  moulding  board  to  strengthen 
the  plaster  profile,  and  on  which  it  is  run.  The  board 
may  be  made  in  two  or  more  pieces,  each  about  1  inch 
thick,  and  in  width  according  to  the  depth  of  the  mould- 
ing, and  in  length  as  required,  the  whole  being  held 
together  by  cleats  H,  which  are  nailed  about  3  or  4  feet 
apart.  Broad-headed  nails  are  then  driven  in  at  ran- 
dom, leaving  the  heads  projecting,  to  give  a  key  for 
the  plaster  profile  P.  The  profile  is  then  run  with  a 
reverse  running  mould.  It  will  be  seen  that  this  profile 
is  undercut,  therefore  a  loose  piece  L  is  required  to 
enable  the  mould  to  draw  off  the  moulding.  The  re- 
verse mould  and  loose  piece  are  constructed  iu  the  same 
way  as  described  under  the  heading  of  ''Reverse  Mould- 
ings.'^ It  may  be  here  remarked  that  it  is  sometimes 
useful  to  have  an  ''eye"  inserted  in  the  loose  piece  to 
give  a  better  hold  for  the  fingers  when  taking  the  loose 
piece  off  the  moulding.  The  eyes  are  made  by  twisting 
a  piece  of  strong  wire  round  the  handle  of  a  tool  bruch, 
leaving  one  end  in  the  form  of  a  ring,  and  the  other 
bent  outwards  so  as  to  form  a  key.  The  eyes  are  fixed 
about  3  or  4  feet  apart,  the  fixing  being  done  by  cut- 
ting a  hole  in  the  loose  piece  and  bedding  the  shank  of 
the  eye  with  plaster,  and  then  cutting  a  slot  in  the 
main  part  of  the  mould  to  receive  the  ring  of  the  eye 


HOW  TO  USE  THEM 


441 


as  shown  at  E.  The  mould  is  held  in  position  by  the 
bracket  B,  fixed  4  or  5  feet  apart.  The  mould  is  further 
secured  by  the  stay  S,  the  other  or  inner  end  of  the 
stay  is  fixed  on  to  the  main  wall.  It  will  be  understood 
that  a  plaster  mould  for  this  purpose  should  be  dry  and 
hard,  and  then  well  seasoned  with  linseed  oil,  or  with 
a  hot  solution  of  paraffin  wax.  After  the  mould  is  fixed 
in  position  it  is  oiled,  and  then  the  concrete  C  is  filled 
in,  taking  care  that  the  surface  of  the  mould  is  first 
covered  with  a  thin  coat  of  neat  cement.  The  mould 
may  be  oiled  with  paraffin  oil;  but  if  the  mould  is  in- 
clined to  stick/'  oil  it  with  chalk  oil/'  i.  e.,  paraffin 
oil  and  French  chalk,  about  the  consistency  of  cream. 

When  the  concrete  is  set,  the  brackets  are  removed, 
and  the  mould  taken  off.  The  mould  in  this  case  would 
draw  in  the  line  of  the  arrow  A.  The  loose  piece  is 
then  taken  off.  It  is  here  that  the  use  of  the  eyes  will 
be  found.  Before  removing  the  brackets  it  is  advisable 
to  prop  the  mould,  in  case  it  may  drop  off  and  break 
the  fragile  portions  of  the  mould  or  parts  of  the  cornice. 
A  heavy  mould  hanging  in  this  position,  especially  if 
the  profile  is  flat,  or  in  good  working  order,  is  apt  to 
drop,  hence  the  necessity  of  props.  If  the  mould  clings, 
or,  as  more  generally  called,  ^'sticks  fast,''  gentle  tap- 
ping with  a  heavy  hammer  will  ease  or  spring  it,  and 
allow  it  to  be  taken  off.  A  heavy  hammer  is  more  ef- 
fective in  making  the  mould  spring  than  a  light  ham- 
mer, as  the  force  required  for  a  light  hammer  is  apt  to 
injure  the  mould.  This  is  why  a  heavy  hammer  with  a 
flat  head  is  best  for  plaster  piece  moulding. 

Eig.  2  is  the  section  of  a  string  moulding  with  the 
casting  mould  and  bracket.  A  chase  is  formed  in  the 
brickwork  to  allow  it  to  bond,  and  the  joints  and  the 


442  CEMENTS  AND  CONCRETES 


surface  of  the  brickwork  are  cut  out  and  hacked  to  give 
a  further  key  to  the  moulding.  M  is  the  mould  (in  this 
case  made  of  wood).  The  profile  is  drawn  without  any 
undercut  parts,  so  as  to  allow  the  mould  to  draw  off  in 
one  piece.  B  is  the  bracket^  and  C  is  the  concrete.  The 
same  directions  for  casting  Fig.  1  apply  to  this  and 
the  other  moulding  here  shown.  A  drip  member,  as 
shown  at  the  top  member  of  both  cornices,  is  generally 
used  for  exterior  mouldings^  to  prevent  the  water  run- 
ning over  the  wall  surface. 

Fig.  3  is  the  section  of  a  wall  coping  and  the  casting 
mould.  M  is  the  mould,  a  similar  one  being  used  for 
the  other  side.  A  mould  for  this  purpose  is  best  formed 
with  flooring  boards  about  1  inch  thick,  and  fixing  them 
together  as  shown.-  The  drip  D  is  readily  formed  by 
sawing  an  inch  bead  through  the  centre,  and  nailing  it 
on  the  bottom.  Two  forms  of  brackets,  B  and  B,  are 
here  given.  One  is  cut  out  of  the  solid,  and  the  other 
made  of  two  pieces  of  wood  nailed  together. 

Fig.  4  is  the  section  of  a  casting  mould  for  a  saddle- 
back coping.  R  is  a  quarter-round  piece  of  wood  fixed 
in  the  angle  of  the  mould  to  form  a  cavetto,  which  is 
sometimes  used  in  copings.  D  is  an  angular-shaped 
drip,  sometimes  used  in  place  of  a  circular  one.  T  is 
part  of  a  template  used  for  forming  the  saddle-back  of 
the  coping. 

Fig.  5  is  the  section  of  a  mould  for  a  coping  with 
splayed  or  chamfered  angles.  S  is  a  triangular  strip 
of  wood  fixed  in  the  angle  and  the  top  of  the  mould  to 
form  the  splays,  and  D  is  a  circular  drip. 

Concrete  mouldings  that  are  deeply  undercut  or  in- 
tricate in  profile  may  be  cast  in  situ  by  the  use  of  the 
''Waste  Mould  Process.^' 


HOW  TO  USE  THEM 


443 


Modelling  in  Fine  Concrete. — Figures  of  the  humaii 
and  animal  form,  also  emblems,  trade  signs,  and  build- 
ings, are  now  being  made  in  fine  concrete.  The  work 
may  be  executed  in  situ,  or  in  the  moulding  shop,  and 
then  fixed  in  position.  For  important  works  a  plaster 
model  is  first  made,  and  placed  in  position,  so  as  to 
judge  of  the  effect  before  committing  it  to  the  perma- 
nent material.  For  this  purpose  the  model  is  first 
modelled  in  clay,  and  then  it  is  waste-moulded,  and  a 
plaster  cast  obtained.  After  the  model  is  approved  it 
is  moulded,  and  then  cast  in  the  fine  concrete.  The 
material  is  composed  of  Portland  cement,  and  a  light, 
but  strong,  aggregate ;  and  the  cast  is  made  in  a  similar 
way  to  that  described  for  casting  vases.  The  material 
may  be  colored  as  required  to  suit  the  subject.  The 
general  method  of  executing  figures  ^^on  the  round'' 
in  fine  concrete  or  Portland  cement  is  to  model  the 
figure  direct  in  the  cement  on  an  iron  frame,  and  then 
to  fix  it  in  its  permanent  position.  This  is  effected  b}^ 
first  making  a  full-sized  sketch  of  the  proposed  figure, 
then  setting  out  on  this  the  form  of  the  necessary  iron- 
work to  serve  as  frame  or  skeleton  to  form  an  internal 
support.  This  iron  frame  also  forms  a  core  to  enable 
the  figure  to  be  made  hollow,  and  serves  as  a  .  permanent 
support  for  thin  parts  and  extremities  of  the  figure. 
The  quantity,  size,  and  form  of  the  iron  frame  is  regu- 
lated by  the  size,  form,  and  position  of  the  figure.  For 
instance,  if  the  model  of  a  full-size  lion  is  required,  first 
make  a  rectangular  frame  to  suit  the  feet  of  the  lion 
and  the  base  on  which  the  figure  stands.  The  .base 
frame  is  made  of  iron  bars,  ly^  inches  wide  by  i/4  i^ch 
thick,  fixed  on  edge.  Then  set  out  four  leg-irons,  and 
connect  them  on  the  base  frame,  and  then  set  out  one 


444  CEMENTS  AND  CONCRETES 


or  two  body-irons,  and  connect  them  with  the  leg-irons. 
After  this  set  out  a  looped  piece  to  fit  the  contour  of 
the  neck  and  head,  and  fix  it  to  the  body-iron.  Now 
set  out  the  tail-iron.  This  is  best  formed  with  an  iron 
pipe,  ^  and  it  should  be  made  to  screw  on  to  the  body- 
iron.  This  allows  the  tail  to  be  unscrewed  when  the 
model  is  finished,  and  screwed  on  afi:er  the  model  is 
fixed  in  position,  thus  enabling  the  model  to  be  more 
freely  handled,  and  with  less  risk  of  breakage  when 
moving  and  fixing  in  its  permanent  position. 

Having  made  the  frame,  place  it  on  a  stout  modelling 
board,  keeping  the  base  frame  from  1  to  3  inches  above 
the  board,  according  to  the  depth  of  the  base ;  the  frame 
being  temporarily  supported  with  four  pieces  of  brick 
or  stone.  This  is  done  to  allow  the  base  frame  to  be 
enveloped  with  concrete.  This  done,  fix  wood  rules,  cut 
to  the  depth  of  the  base,  on  the  board,  so  as  to  form 
a  fence  on  all  sides  of  the  base.  Then  fill  in  the  base 
with  concrete ;  and  when  this  is  set,  proceed  with  the 
coring  out,  so  as  to  obtain  a  hollow  model. 

In  order  to  decrease  the  weight  of  concrete  figures 
'^on  the  round,''  and  to  enable  them  to  be  more  easily 
handled  and  hoisted  when  fixing  them  in  their  perma- 
nent positions,  they  should  be  made  hollow.  This  is 
effected  by  making  a  round  skeleton  frame  with  hoop- 
iron,  or  with  wire-netting,  for  the  body,  neck,  and  head, 
and  other  thick  parts.  This  metal  skeleton  must  be 
built  on  and  securely  fixed  to  the  main  iron  frame.  The 
whole,  or  parts  of  the  figure,  may  also  be  cored  out  with 
shavings  or  tow,  and  held  in  position  with  tar  bands  or 
canvas  strips,  dipped  in  plaster.  Tow  is  an  excellent 
material  for  forming  cores.  By  making  up  the  inner 
parts  with  dry  tow^  and  then  dipping  tow  in  plaster  for 


HOW  TO  USE  THEM 


445 


the  outside  coat,  the  core  can  be  made  to  any  desired 
shape,  and  also  leave  the  necessary  thickness  for  the 
concrete.  To  prevent  the  material  slipping  down  by 
its  own  weight,  pieces  of  iron  or  wood,  in  the  form  of 
crosses,  are  fastened  with  copper  wire  or  tar  rope  to 
the  iron  rods,  which  are  used  as  single  supports.  These 
iron  or  wood  pieces  must  be  fixed  in  all  directions,  and 
in  such  a  way  that  the  material  is  held  up  by  them. 
For  small  extremities,  such  as  fingers  of  human  figures, 
beaks  of  birds,  fins  of  fishes,  horns  and  tails  of  animals, 
iron  rods  should  be  fixed  on  the  main  frame,  and  the 
parts  to  be  covered  with  cement  must  be  notched  or 
bound  at  intervals  with  copper  wire  or  tar  rope.  The 
distance  between  the  core  and  the  finished  face  of  the 
figure  is  of  course  the  actual  thickness  of  the  model. 
This  thickness  may  vary  from  1  inch  to  3  inches,  or 
even  4  inches  at  some  parts.  An  actual  thickness  of  2 
inches  will  be  sufficient  to  give  the  requisite  strength. 

When  the  core  is  made,  cover  it  with  a  coat  of  Port- 
land cement  and  old  lime  putty,  in  the  proportion  of  3 
of  the  former  to  1  of  the  latter,  and  add  sufficient  tow 
or  hair  to  give  tenacity.  If  there  are  open  spaces  in 
the  skeleton  iron  work,  bridge  them  over  with  bits  of 
tiles  and  cement.  The  whole  surface,  after  being  coated, 
must  be  well  scratched  with  a  nail,  to  give  a  key  for 
the  roughing  out  coat.  This  scratched  coat  must  be 
allowed  to  set  before  proceeding  with  the  actual  model- 
ling. The  stuff  for  roughing  out  is  composed  of  2 
parts  of  Portland  cement  and  1  part  of  fine  aggregate. 
Crushed  bricks,  stone,  or  pottery  ware  passed  through 
a  sieve  having  a  %  inch  mesh  may  be  used  as  aggre- 
gates. The  finishing  stuff  is  composed  of  fine  sifted 
Portland  cement.    The  addition  of  a  fifth  part  of  old 


446  CEMENTS  AND  CONCRETES 


lime  putty  to  the  cement  makes  the  stuff  more  mellow, 
and  works  freer  and  sweeter.  The  modelling  is  done  as 
described  for  in  situ  work.  The  finishing  coat  can  be 
colored  to  any  desired  tint,  as  already  described. 

Concrete  Fountains^ — Fine  concrete  is  an  excellent 
material  for  the  construction  of  fountains.  It  is  ob- 
vious that  a  vast  amount  of  cutting  and  consequent 
waste  of  material  is  involved  in  the  executing  of  foun- 
tains, ^^on  the  round,*"  when  natural  stone  is  employed. 
Saving  of  material,  and  a  corresponding  reduction  in 
the  cost,  is  effected  by  use  of  a  material  that  can  be 
easily  cast,  and  is  at  the  same  time  durable  and  im- 
pervious. These  qualities  combined  are  found  in  arti- 
ficial stone  composed  of  fine  concrete.  Being  readily 
made  in  large  blocks  (any  sized  basin  can  be  made  in 
one  piece),  there  is  no  jointing  required,  as  is  the  case 
with  terra  cotta,  which  is  another  form  of  artificial 
stone.  Fountains  composed  of  fine  concrete  are  made 
in  a  similar  way  to  that  described  for  making  and  cast- 
ing vases. 

Concrete  Tanks, — Concrete  tanks  to  contain  water, 
and  for  a  variety  of  manufacturing  purposes,  are  now 
largely  in  use.  They  are  strong  and  durable,  and  hav- 
ing hard  smooth  surfaces,  they  are  easily  washed  and 
kept  clean.  Being  impervious  to  vermin,  damp,  and 
atmospheric  influences,  they  are  the  coolest  and  most 
sanitary  water  cisterns  that  can  be  used.  Cattle  troughs 
are  best  made  in  concrete.  Concrete  tanks  have  been 
used  as  water  and  silicate  baths  for  indurating  con- 
crete casts,  and  during  their  constant  use  for  over  a 
decade  no  signs  of  cracks  or  damp  are  visible.  They 
were  made  in  one  piece,  varying  in  size  from  6  feet  up 
to  18  feet  long,  3  feet  to  7  feet  wide,  2  feet  6  inches  to 


HOW  TO  USE  THEM 


447 


4  feet  high^  and  from  3  to  4^2  inches  thick.  Some  were 
castj  but  the  large  ones  were  made  in  situ.  The  method 
of  construction  (for  in  situ  work)  being  simple  and  ex- 
peditious, the  total  cost  is  small.  For  a  tank  9  feet  long, 
4  feet  6  inches  wide,  2  feet  6  inches  high,  and  3^/2  inches 
thick,  first  frame  up  wood  sides  and  ends  to  the  above 
length,  width,  and  height,  then  make  inside  boards, 
the  lengths  and  widths  being  the  same  as  above,  less 
the  tank  thickness,  and  the  heights  less  the  bottom 
thickness.  The  sides  and  ends  are  hung  by  means  of 
cross  battens  laid  on  the  upper  edges  of  the  outside 
framing,  and  kept  in  position  with  inside  stays.  This 
leaves  an  open  and  continuous  space  at  the  sides,  ends, 
and  bottom.  The  constructive  materials  are  1  part  of 
Portland  cement  and  2  of  fine  slag  or  granite,  gauged 
stiff,  and  laid  over  the  bottom.  Next,  the  open  sides 
and  ends  are  filled  up,  taking  great  care  that  the  whole 
mass  is  thoroughly  consolidated  by  ramming.  The 
stuff  for  the  sides  and  ends  should  be  laid  in  layers 
from  6  to  8  inches  deep,  each  layer  being  well  rammed 
before  the  next  is  laid. 

The  angles  are  strengthened  by  inserting  angle  irons 
during  the  process  of  filling  in.  As  soon  as  the  concrete 
is  set  the  inner  boards  are  removed,  and  if  the  surface 
is  smooth  or  dry,  it  must  be  keyed  with  a  coarse  drag 
or  a  sharp  hand  pick.  It  is  then  swept  and  wetted  to 
cleanse  it  and  stop  the  suction,  so  as  to  ensure  perfect 
cohesion,  and  allow  the  final  coat  to  retain  its  moisture 
during  the  process  of  trowelling  and  the  stuff  setting. 

The  finishing  coat  is  composed  of  neat  cement,  the 
finer  ground  the  better,  as  percolation  through  con- 
crete made  with  a  finely  ground  cement  is  less  liable 
than  when  made  with  a  coarsely  ground  cement. 


448  CEMENTS  AND  CONCRETES 


The  final  coat  is  laid  about  3/16  inch  thick^  and  pre- 
ceded by  brushing  the  surface  with  liquid  cement  to 
fill  up  all  crevices,  and  afford  better  adhesion  between 
the  surface  and  the  final  coat.  When  the  stuff  is  firm, 
it  is  well  trowelled  to  a  fine  and  close  surface.  The 
outer  boards  are  then  removed,  and  the  surface  finished 
in  a  similar  way. 

Concrete  Sinks. — Concrete  sinks  can  be  made  to  any 
desired  size  or  form.  They  are  cast  in  wood  or  plaster 
moulds,  and  are  composed  of  1  part  of  Portland  cement 
to  2  parts  of  fine  crushed  granite  or  other  hard  aggre- 
gate. They  are  made  with  rebated  holes  for  traps.  The 
ordinary  size  are  as  follows :  2  feet  6  inches  by  1  foot 
8  inches ;  2  feet  9  inches  by  1  foot  8  inches ;  and  3  feet 
by  2  feet,  all  6  inches  deep,  and  from  2  to  3  inches  thick. 

Garden  Edging. — Plain  and  ornamented  edgings  are 
now  made  in  concrete.  They  are  made  in  various 
lengths.  The  most  useful  size  is  3  feet  long,  6  inches 
deep^  and  2  inches  thick.  They  can  be  made  to  any 
curve,  and  tinted  to  any  shade. 

Concrete  Vases. — During  the  last  half-century  thou- 
sands of  vases,  composed  of  fine  concrete — commonly 
called  artificial  stone'' — have  been  used  for  the  dec- 
oration of  buildings  and  practical  use  in  gardens,  con- 
servatories, &c.  For  vases  that  are  cast  in  sections  the 
thickness  of  large  and  open  parts,  such  as  the  ^'body, " 
are  regulated  by  means  of  a  plaster  core,  which  is 
placed  in  the  open  mould.  The  contour  of  the  core 
must  be  so  arranged  that  the  cast  will  draw  from  the 
core,  or  vice  versa.  For  some  forms  of  vases,  the  core 
must  be  made  in  pieces  similar  to  a  piece  mould.  The 
method  of  making,  moulding,  and  casting — the  latter 
by  the  aid  of  a  template  instead  of  a  cores 


HOW  TO  USE  THEM 


449 


Concrete  Mantel  Pieces. — Chimney-pieces  of  all  sizes 
and  shapes  are  now  extensively  made  in  fine  concrete. 
They  are  generally  made  in  wood  moulds,  plaster 
moulds  being  let  in  the  main  mould  for  ornamental 
parts.   They  are  often  made  in  colored  concrete. 

Colored  Concrete. — Concrete  casts,  also  work  laid  in 
situ,  can  be  colored  to  imitate  any  natural  stone.  This 
is  effected  by  mixing  mineral  oxides  of  the  required 
color  with  the  cement  used  for  the  surface  coat.  The 
color  coat  should  not  exceed  %  inch  in  thickness,  as 
oxides  are  too  expensive  to  use  for  the  entire  thickness 
of  the  cast.  The  quantity  of  oxide  to  be  added  to  the 
cement  depends  upon  the  strength  of  the  oxide.  Some 
are  much  stronger  than  others.  Five  per  cent,  of  a 
strong  oxide  will  impart  a  close  resemblance  of  the 
desired  color  to  the  concrete,  but  a  weak  oxide  will  re-° 
quire  from  10  to  15  per  cent.,  and  even  20  per  cent.,  to 
obtain  the  same  color.  Some  of  the  red  oxides  range 
in  color  from  scarlet  or  Turkey  red,  gradually  deepen- 
ing to  chocolate.  Some  oxides  contain  95  per  cent,  of 
pure  ferric  oxide,  w^hich  is  made  from  copperas,  or, 
scientifically  speaking,  sulphate  of  iron.  This  is  a  by- 
product, and  is  frequently  evolved  from  waste  acid 
liquors  at  tinplate  works,  and  is  obtained  in  large  quan- 
tities from  South  Wales.  This  kind  of  oxide  is  far 
more  suitable  for  coloring  concrete  than  ochres  and 
most  of  the  earthy  oxides.  Earthy  colors,  like  Venetian 
red  and  umber,  soon  fade  and  have  a  sickly  appearance. 
The  oxides  should  be  intimately  mixed  with  the  cement 
in  a  dry  state  before  it  is  gauged.  The  mixing  is  gen- 
erally done  by  hand,  but  better  results  are  obtained  by 
the  use  of  grinding  machine.  It  is  a  safe  plan  to  try 
various  proportions  of  color  and  cement  and  gauge 


450  CEMENTS  AND  CONCRETES 


small  parts,  and  when  set  and  dry  select  those  most 
suitable  for  the  desired  purpose.  All  cast  work,  as  soon 
as  extracted  from  the  moulds,  should  be  examined,  and 
any  blubs  stopped  and  chipped  parts  or  other  minor 
defects  made  good  while  the  work  is  moist  or  green, 
using  neat  cement  and  colors  in  the  same  proportion 
as  used  for  the  surface  stuff.  Colored  surfaces  may  be 
greatly  improved  by  brushing  the  cast  as  soon  as  set 
with  a  solution  of  the  same  color  as  used  for  the  sur- 
face coat.  A  color  solution,  made  by  mixing  the  color 
with  water  and  a  solution  of  alum,  is  very  useful  for 
coloring  Portland  cement,  with  or  without  sand.  If  this 
coloring  solution  is  brushed  over  the  surface  while  it 
is  moist  or  semi-dry,  a  good  standing  color  can  be  ob- 
tained without  mixing  color  with  dry  cement.  This 
method  will  be  found  useful  for  sgraffitto,  &c. 

A  novel  and  color-saving  method,  for  coloring  the 
upper  surfaces  of  slabs  or  other  flat  casts,  is  effected 
by  first  filling  in  the  mould  in  the  usual  way,  then 
placing  the  colored  cement  in  a  dry  state  in  a  hand 
sieve,  and  then  violently  shaking  or  tapping  the  sides 
of  the  sieve^  so  as  to  sprinkle  the  colored  cement  uni- 
formly over  the  surface  until  it  is  nearly  1/16  inch 
thick.  The  surface  is  then  trowelled  in  the  usual  way. 
The  sprinkling  must  be  done  as  soon  as  the  main  body 
of  the  stuff  is  ruled  off,  so  as  to  obtain  a  homogeneous 
body.  Another  and  a  novel  method  which  may  be  ad- 
vantageously employed  for  finishing  slab  or  other  large 
surfaces  in  a  mould  is  as  follows :  A  fine  finished  face 
is  more  readily  obtained  by  using  a  smoothing  knife 
(for  brevity  termed  a  shaver")  than  by  a  trowel.  A 
shaver  is  a  piece  of  polished  steel  about  3  inches  wide 
and  %  inch  thick,  the  length  being  regulated  according 


HOW  TO  USE  THEM  *  451 


to  the  width  of  the  mould,  and  allowing  about  8  inches 
at  each  end  for  handles.  For  instance,  for  a  slab  2  feet 
wide,  the  shaver  should  be  3  feet  long.  This  allows  2 
feet  for  the  surface  of  the  cast,  3  inches  to  bear  on  the 
rims  of  the  mould,  each  1  V>  inches  wide ;  8  inches  for 
the  handles,  each  4  inches  long;  and  1  inch  for  play. 
One  edge  or  side  is  cut  to  an  angle  of  45°,  so  as  to 
form  a  cutting  edge.  The  method  of  filling  in,  coloring, 
and  finishing  the  surface  of  the  slab  is  as  follows :  First 
fill  in  the  mould  with  the  concrete,  ramming  and  beat- 
ing it  as  already  described  until  the  stuff  is  about  1/16 
inch  above  the  mould  rims,  then  clean  off  the  stuff  on 
the  rims  with  a  wood  template  (rebated  to  fit  the  width 
of  the  rims),  and  lay  the  shaver  flat  on  the  rims,  keep- 
ing the  cutting  edge  outwards,  and  then  push  it  for- 
ward, keeping  it  flat  on  the  rims,  so  as  to  shave  off  the 
superfluous  stufit".  This  done,  sprinkle  the  colored  ce- 
ment, Avith  the  aid  of  a  sieve,  until  about  1/16  inch 
thick;  then  clean  the  rims  again,  and  pass  the  shaver 
forwards  and  backwards  twice  or  thrice,  which  will 
leave  a  straight,  smooth,  and  uniform-colored  surface. 
This  method  effects  a  considerable  saving  in  the  amount 
of  oxide  and  of  time.  The  thickness  of  the  coloring 
stratum  is  reduced  mechanically  to  the  minimum  (about 
1/32  inch),  which  is  all  sufficient  for  coloring  purposes 
where  the  surface  is  not  subjected  to  frictional  wear. 

As  already  mentioned,  bullocks'  blood  mixed  with 
cement  gives  a  near  resemblance  to  red  brick,  but  it  is 
not  a  desirable  material  to  work  with,  and  the  same 
effect  can  be  obtained  by  the  use  of  red  oxides.  Red 
sand,  brick,  and  stone,  all  finely  ground,  have  been  em- 
ployed for  coloring  cement  surfaces^  but  if  too  fine  or 
in  large  quantities  they  weaken  the  surface;  and  if 


452  CEMENTS  AND  CONCRETES 


coarse-grained  they  possess  little  coloring  effect,  be- 
cause the  particles  are  liable  to  show  singly,  causing  a 
spotty  appearance,  or  the  cement  entirely  covers  the 
surface  of  each  particle  of  sand.  Powdered  glass,  mar- 
ble, flint,  alabaster,  metal  filings,  and  mineral  coloring 
can  be  effectively  employed  for  coloring  concrete  sur- 
faces by  mixing  with  the  cement  used  for  the  surface 
coat.  The  surface  is  improved  by  rubbing  and  stoning, 
also  polishing,  after  the  work  is  dry.  ,Other  methods 
and  quantities  of  colors  for  coloring  Portland  cement 
surfaces  are  given. 

Fixing  Blocks. — Concrete  fixing  blocks  do  not  shrink, 
warp,  or  rot.  Consequently  they  are  superior  to  wood 
fillets,  &c.  They  are  principally  used  in  concrete  floors, 
stair  landings,  and  walls,  as  bearings  and  fixing  points 
for  wire-lathing  and  fibrous  plaster  work.  Floor  boards 
may  also  be  fixed  to  them.  They  are  also  built  into 
brick  walls  for  similar  purposes,  as  well  as  for  external 
wall  tilings.  For  ceilings,  stair  soffits,  and  landings, 
the  blocks  are  laid  on  the  centrings  where  required, 
and  permanently  secured  by  laying  concrete  between 
and  over  them.  For  bearings  and  fixing  flooring  boards, 
they  are  secured  flush". 

TYPICAL  SYSTEMS  OF  REINFORCED  CONCRETE 
CONSTRUCTIONS  FROM  VARIOUS  SOURCES. 

Of  the  interesting  features  of  modern  civil  engineer- 
ing, interesting  because  of  their  extreme  novelty  and 
successful  application,  reinforced  concrete  is  probably 
most  noteworthy  because  of  its  unique  adaptability. 
How  striking  is  the  influence  of  steel  reinforcement  is 
best  exemplified  by  a  reference  to  Fig.  1.    There  tw  j 


HOW  TO  USE  THEM 


453 


beams  are  shown  designed  to  carry  ordinary  floor  loads, 
the  one  made  entirely  of  concrete  and  the  other  of  con- 
crete with  a  sheet  of  expanded  metal  imbedded  in  the 
tensile  portion  of  the  beam.  The  saving  in  mere  weight 
of  concrete  alone  is  apparent ;  and  when  we  remember 
that  the  adoption  of  floor  beams  entirely  of  concrete 
means  an  increase  of  thickness  of  nine  inches  or  as- 
suming flve  to  eight  floors,  an  increase  in  the  total 
height  of  the  building  (with  extra  cost  and  heavier 
walls,  together  with  heavier  foundations  to  carry  them) 
of  from  four  to  six  feet,  we  see  that  even  as  regards 
initial  outlay  for  materials,  the  introduction  of  settle 
reinforcement  into  concrete  construction  is  of  import- 
ance. 

So  far  as  economy  in  initial  cost  of  materials  is  con- 
cerned, reinforced  concrete  is  undoubtedly  cheaper 
than  either  concrete  or  steel  alone.  It  is  not  very  easy 
to  demonstrate  this  economy  except  by  comparative 
cost  in  individual  cases,  but  an  approach  to  a  systematic 
comparison  has  been  made  by  Mr.  Walter  Loring  Webb, 
as  follows :  A  cubic  foot  of  steel  weighs  490  pounds. 
Assume  as  an  average  price  that  it  can  be  bought  and 
placed  for  4.5  cents  per  pound.  The  steel  will  therefore 
cost  $22.05  per  cubic  foot.  On  the  basis  that  concrete 
may  be  placed  for  $6  per  cubic  yard,  the  concrete  will 
cost  22  cents  per  cubic  foot  which  is  1  per  cent  of  the 
cost  of  the  steel.  Therefore,  on  this  basis  if  it  is  neces- 
sary to  use  as  reinforcement  an  amount  of  steel  whose 
volume  is  in  excess  of  1  per  cent  of  the  additional  con- 
crete which  would  do  the  same  work,  there  is  no  econ- 
omy in  the  reinforcement,  even  though  the  reinforce- 
ment is  justified  on  account  of  the  other  considerations. 
Assuming  500  pounds  per  square  inch  as  the  working 


454  CEMENTS  AND  CONCRETES 


compressive  strength  of  concrete^  and  16,000  as  the  per- 
missible stress  in  steel,  it  requires  3.125  per  cent  of  steel 
to  furnish  the  same  compressive  stress  as  concrete.  On 
the  above  basis  of  cost,  the  compression  is  evidently 
obtained  much  more  cheaply  in  concrete  than  in  steel 
— in  fact,  at  less  than  one-third  of  the  cost.  On  the 
other  hand^  even  if  we  allow  50  pounds  per  square  inch 
tension  in  the  concrete  and  16,000  pounds  in  the  steel, 
it  requires  only  0.21  per  cent  of  steel  to  furnish  the 


i  w 


Pig.  l.-;^These  Beams  Are  Designed  to  Carry  the  Same 
Load.   The  Upper  is  of  Reinforced  Concrete,  the 
Lower  of  Plain  Concrete. 

same  strength  as  the  concrete,  which  shows  that,  no 
matter  what  may  be  the  variation  in  the  comparative 
price,  of  concrete  and  steel,  steel  always  furnishes  ten- 
sion at  a  far  cheaper  price  than  concrete,  on  the  above 
basis  at  less  than  one-third  of  the  cost.  The  practical 
meaning  of  this  is^  on  the  one  hand,  that  a  beam  com- 
posed wholly  of  concrete  is  usually  inadvisable,  since  its 
low  tensile  strength  makes  it  uneconomical,  if  not  actu- 
ally impracticable,  for  it  may  be  readily  shown  that, 
beyond  a  comparatively  short  span,  a  concrete  beam 
will  not  support  its  own  weight.    On  the  other  hand^ 


HOW  TO  USE  THEM  455 

on  account  of  the  cheaper  compressive  stress  furnished 
by  concrete,  an  all-steel  beam  is  not  so  economical  as 


Fiff.  2— Types  of  Steel  Reinforcin«:  Rods, 

a  beam  in  which  the  concrete  furnishes  the  compres- 
sive stress  and  the  steel  furnishes  the  tensile  stress. 


Fig.  3.— A  Reinforced  Concrete  Pier  for  Railway 
Traffic' 


This  statement  has  been  very  frequently  verified  when 
comparing  the  cost  of  the  construction  of  floors  de- 


456  CEMENTS  AND  CONCRETES 


signed  by  using  steel  I-beams  supporting  a  fire-proof 
concrete  floor,  and  that  of  a  concrete  floor  having  a 
similar  floor  slab  but  making  the  beams  as  T-beams  of 
reinforced  concrete. 

A  good  idea  of  reinforced  concrete  construction  can 
be  obtained  from  Fig.  3,  which  is  an  isometrical  pro- 
jection of  a  portion  of  a  pier  strong  enough  to  carry 
the  heaviest  railway  traffic.  The  disposition  of  the 
steel  work  is  shown  in  the  piles,  the  main  girders,  and 
beams;  and  the  manner  in  which  the  steel  rods  run- 
ning along  the  tensile  or  bottom  side  of  the  girders 
and  beams  are  bent  up  over  the  top  of  the  pile,  which 
is  here  the  tensile  member  (the  beams  being  continu- 
ous), and  then  down  again  to  the  bottom  of  the  girders 
and  beams,  is  most  instructive. 


Fi^.  4.— Method  of  Joining  Columns  and  Floors. 


The  sections  of  the  steel  employed  vary  in  different 
systems,  being  round,  flat,  square,  angle,  and  tee — Fig. 
2.  In  all  cases  the  simplest  section  is  the  best,  as  it 
costs  less,  and  readily  allows  the  concrete  to  be  rammed 
into  the  closest  contact  with  the  entire  surface  of  the 
armoring.  In  America  the  Eansome  system  is  most 
extensively  used — a  system  in  which  a  bar  of  twisted 


HOW  TO  USE  THEM 


457 


steel  is  employed.  Small  sections  are  better  than  large 
ones,  for  by  their  use  we  obtain  a  more  uniform  dis- 
tribution of  stress  in  the  steel;  we  can  also  readily 
bend  and  work  them  into  any  required  shape;  and 
finally  the  most  economical  disposition  of  material  is 
obtained,  the  metal  being  placed  at  the  maximum  dis- 
tance from  the  neutral  axis. 


Expanded  metal  meshing  (Fig.  6)  is  increasingly  em- 
ployed, more  particularly  m  the  lighter  forms  of  con- 
struction. It  consists  of  sheets  of  metal  which  have 
been  mechanically  slit  and  expanded,  so  as  to  produce 
a  network.  This  type  of  reinforcement  has  many  and 
obvious  advantages.  Its  mere  existence  is  proof  of  good 
steel,  and  it  forms  an  excellent  key  for  concrete  too 
thin  to  permit  reinforcement  in  the  form  of  rods ;  thus 
it  is  very  useful  for  concrete  plaster,  ceiling,  and  parti- 
tion wall  work.  A  good  example  of  reinforced  con- 
crete in  which  expanded  metal  is  used  may  be  found 
in  the  Monier  system  (Fig.  5).    An  improvement  on 


Fig.  5.— The  Monier  System, 


458  CEMENTS  AND  CONCRETES 


this  system  is  the  Clinton  method  (Fig.  11)  of  using 
an  electrically  welded  wire  netting  in  combination  with 
concrete.  Clinton  fabric  consists  of  drawn  wire  of  6 
to  10  gauge,  which  may  be  made  in  lengths  up  to  300 
feet.  The  system  is  therefore  a  continuous  bond  system, 
which  prevents  the  entire  collapse  of  a  span  unless  the 
weight  imposed  is  sufficient  to  break  all  the  wires. 


Fi^4  07— Expanded  Metal. 


-  Columns  and  Piles. — Reinforced  columns  are  made 
with  either  square,  rectangular,  or  circular  sections. 
They  are  reinforced  with  from  four  to  twenty  rods,  the 
diameters  of  which  vary  from  %  to  2^/2  inches.  The 
rods  are  placed  as  nearly  as  practicable  to  the  circum- 
ference of  the  column,  so  as  to  give  the  greatest  radius 
of  gyration  for  the  section ;  but  they  are  never  placed 
so  near  the  surface  that  they  have  not  at  least  one  or 
two  inches  protective  covering.  The  steel  so  disposed 
is  able  to  take  up  the  tensile  stresses  which  may  be 


HOW  TO  USE  THEM 


459 


induced  in  the  column  by  eccentric  loading,  lateral 
shocks  wind  pressure,  and  the  pull  of  belting. 

Columns  and  piles  are  made  in  wooden  boxes,  each 
consisting  of  three  permanent  sides  and  a  fourth  side 
which  is  temporary  and  removable.  Under  the  patent 
rights  of  Francois  Hennebique  the  reinforcing  is  placed 


Ifig.  7.  -£aiisome  iSysslem  of  Erecting  Colamns* 


in  these  boxes,  and  adjusted  by  gauges  to  within  one  or 
two  inches  of  the  sides.  The  concrete  is  laid  and 
rammed,  about  six  inches  at  a  time,  with  small  hand 
rammers.  The  open  side  of  the  box  is  built  up  by 
battens  fitting  into  grooves  in  the  permanent  sides,  as 
the  work  proceeds ;  this  enables  inspection  of  the  work 


460  CEMENTS  AND  CONCRETES 

to  be  made,  and  facilitates  the  placing  of  the  ties  at  the 
proper  positions.   The  ties  are  made  of  round  wire  3/16 


Fig.  8»— Wood  Centering  and  Ransome  Steel  Bars  for  50-t*oot 
Floor  Span* 


inch  diameter  and  are  dropped  down  over  the  top  of 
the  steel  rods.    They  are  spaced  down  two-inch  centres 


HOW  TO  USE  THEM 


461 


at  the  bottom  and  top,  to  twelve-inch  centres  in  the 
centre  of  length  of  the  column,  and  are  intended  to 
prevent  the  steel  rods  from  spreading  out  under  the, 
action  of  longitudinal  loads.  Fig.  4  shows  the  method 
of  joining  columns  to  the  floor. 


Fig.  9#— Concrete  Power  Plant  in  Course  of 
Construction, 


In  the  Ransome  columns  as  exemplified  in  a  recently 
constructed  factory  building  (Fig.  7),  the  vertical  re- 
inforcement consists  of  round  rods  with  the  connections 
made  about  12  inches  above  the  floor  line ;  in  order  that 


462  CEMENTS  AND  CONCRETES 

these  rods  might  be  continuous  the  ends  were  threaded 
and  connected  with  sleeve  nuts,  thereby  developing  the 
full  strength  of  the  rods.  Horizontal  reinforcement 
was  also  u.sed,  consisting  of  hoops  formed  by  a  spiral 


4^ 


Fig,  10.— Slabs  of  Concrete  Ready  for  Roof. 


made  from  ^4  inch  diameter  soft  wire,  having  a  pitch 
or  spacing  of  4  inches  in  the  basement  columns,  and 
gradually  increasing  to  a  pitch  of  6  inches  in  the  top 
story  (Fig.  12). 

According  to  Mr.  Henry  Longcope  the  first  innova- 
tion in  concrete  piles  was  the  sand  pile,  produced  by 


HOW  TO  USE  THEM  463 


driving  a  wooden  form  in  the 
ground  and  withdrawing  it, 
the  hole  being  filled  with 
moist  sand  well  rammed.  The 
next  method  adopted  was  to 
drive  a  metal  form  into  the 
ground  and  after  withdrawal 
to  fill  the  hole  with  concrete. 
This  was  not  successful,  as  it 
was  open  to  the  serious  objec- 
tion that  on  withdrawing  the 
form,  the  ground  would  col- 
lapse before  the  concrete  could 
be  inserted.  Still  another 
method  was  introduced,  which 
consisted  in  dropping  a  cone- 
shaped  five  ton  weight  a  num- 
ber of  times  from  a  consider- 
able height,  in  order  to  form 
a  hole,  which  was  afterward 
filled  with  concrete.  This 
method  never  passed  the  ex- 
perimental stage.  Coming  to 
more  successful  systems  we 
may  mention  a  method  of 
moulding  a  pile  of  concrete, 
allowing  it  to  stand,  and  then 
driving  it  into  the  ground,  a 
cap  being  used  to  protect  the 
head. 

Of  modern  systems  which 
have  proven  successful,  Gil- 
breth's  pile  must  first  be  re- 


CEMENTS  AND  CONCRETES 


HOW  TO  USE  THEM  465 


corded.  Gilbreth  used  a  molded  corrugated  taper  pile, 
cast  with  core  hole  the  entire  length  of  the  pile,  which  is 
jetted  down  by  a  water  jet  and  finally  settled  by  hammer 
blows. 

Features  which  recommended  the  Gilbreth  piles  are 
the  opportunities  for  complete  inspection  before  driv- 
ing and  the  fact  that  they  save  time  because  they  can 
be  cased  while  excavation  is  going  on.  After  being 
driven  they  can  be  loaded  immediately.  Naturally  they 
present  considerable  skin  friction.  The  making  of  these 
piles  above  the  ground  surface  also  does  away  with  the 
possibility  of  their  being  damaged  or  squeezed  out  of 
shape  by  the  jar  occasioned  by  driving  forms  for  ad- 
joining piles. 

Still  another  method  is  used  by  Raymond.  Under 
this .  system  piles  are  usually  put  in  by  either  of  two 
methods,  the  jetting  method  or  the  pile  core  method. 
The  water  jet  system  is  used  only  where  the  material 
penetrated  is  sand,  quicksand,  or  soft  material  that  will 
dissolve  and  flow  up  inside  the  pile  when  the  water  is 
forced  through  the  pipe,  thus  causing  the  shell  to  settle 
until  it  comes  in  contact  with  the  next  shell,  and  so  on 
until  the  desired  depth  has  been  reached.  The  shells 
are  filled  with  concrete  simultaneously  with  the  sinking 
process,  and  when  necessary  spreads  are  attached  to 
keep  the  hole  in  perfect  line  with  the  pipe.  The  % 
inch  pipe  is  left  in  the  centre  of  the  pile  and  gives  it 
greatly  increased  lateral  strength.  If  desired,  the 
lateral  strength  may  be  further  increased  by  inserting 
rods  near  the  outer  surface  of  the  concrete.  By  this 
method,  piles  of  any  size  up  to  two  feet  in  diameter  at 
the  bottom  and  four  feet  at  the  top  can  be  put  through 


466  CEMENTS  AND  CONCRETES 


any  depth  of  water  and  to  a  suitable  penetration  in 
sand  or  silt  (water  sediment). 

The  pile-core  method  is  the  one  most  generally  used 
for  foundation  work  and  consists  of  a  collapsible  steel 
pile  core,  conical  in  shape,  which  is  incased  in  a  thin, 
tight-fitting  metal  shell.  The  core  and  shell  are  driven 
into  the  ground  by  means  of  a  pile  driver.  The  core 
.  is  so  constructed  that  when  the  desired  depth  has  been 
reached  it  is  collapsed  and  loses  contact  with  the  shell, 
so  that  it  is  easily  withdrawn,  leaving  the  shell  or. cas- 
ing in  the  ground,  to  act  as  a  mold  or  form  for  the 
concrete.  When  the  form  is  withdrawn,  the  shell  or 
casing  is  filled  with  carefully  mixed  Portland  cement 
concrete,  which  is  thoroughly  tamped  during  the  filling 
process. 

The  simplex  system  uses  another  method  in  which 
the  driving  form  consists  of  a  strong  steel  tube,  the 
lower  end  of  which  is  fitted  with  powerful  tooth  jaws, 
which  close  together  tightly,  with  a  point  capable  of 
opening  automatically  to  the  full  diameter  of  the  tube 
while  being  withdrawn.  The  point  of  the  form  closely 
resembles  the  jaws  of  an  alligator.  At  the  same  time 
the  form  is  being  withdrawn,  the  concrete  is  deposited. 

It  is  so  evident  that  concrete  is  vastly  superior  to 
wood  in  the  construction  of  piles  that  it  is  almost  su- 
perfluous to  mention  the  points  of  superiority.  Con- 
crete is  not  subject  to  rot  or  the  ravages  of  the  teredo 
worm,  neither  can  the  piles  constructed  of  concrete  be 
destroyed  by  fire,  and  no  cost  is  attached  for  repairs. 
While  it  is  not  possible  to  give  accurate  statistics  as  to 
the  life  of  a  wooden  pile,  as  it  varies  so  much  under 
different  conditions,  yet  we  know  that  in  some  cases 
a  wooden  pile  is  rendered  worthless  in  a  very  few  years. 


HOW  TO  USE  THEM 


467 


especially  when  the  surrounding  material  is  composed 
of  rotted  vegetation^  or  where  the  pile  is  exposed  by 
the  rise  and  fall  of  tides.  It  is  also  impossible  to  state 
the  exact  cost  of  a  concrete  pile,  as  it  varies  also  ac- 
cording to  conditions.  Ordinarily  speaking,  a  concrete 
pile  will  cost  from  one  and  one-half  times  or  two  times 
as  much  as  a  wooden  pile ;  but  in  order  to  illustrate 
where  a  saving  can  be  made,  the  following  extract  is 
given  from  a  report  on  the  piles  driven  at  the  United 
States  Naval  Academy  at  Annapolis,  Md. : 

'^The  original  plans  called  for  3,200  wooden  piles 
cut  off  below  low  water  with  a  capping  of  concrete. 
To  get  down  to  the  low  water  level  required  sheet  pil- 
ing, shorting  and  pumping,  and  the  excavating  of  near- 
ly 5,000  cubic  yards  of  earth.  By  substituting  concrete 
piles,  the  work  was  reduced  to  driving  850  concrete 
piles,  excavating  1,000  cubic  yards  of  earth  and  placing 
of  1,000  cubic  yards  of  concrete." 

In  the  work  mentioned,  the  first  estimate  for  wooden 
piles  placed  the  cost  at  $9.50  each,  while  the  estimate 
for  concrete  piles  was  placed  at  $20  each,  yet  the  esti- 
mate based  on  the  use  of  wood  piles  aggregated  $52,840, 
while  the  estimate  based  on  the  use  of  concrete  piles 
w^as  $25,403,  or  a  total  saving  in  favor  of  concrete  of 
over  $27,000. 

In  several  instances  piles  have  been  uncovered  to 
their  full  depth,  and  they  were  found  to  be  perfectly 
sound  in  every  particular.  By  surrounding  the  opera- 
tion with  the  safeguards  provided,  it  is  almost  impos- 
sible to  make  a  faulty  pile.  The  concrete  is  made  as 
wet  as  good  practice  will  allow.  Constant  ramming  and 
dropping  the  concrete  from  a  considerable  height  tend 
to  the  assurance  of  a  solid  mass,  then  the  target  on 


468  CEMENTS  AND  CONCRETES 


the  ramming  line  or  the  introduction  of  an  electric  light 
into  the  form  shows  what  is  being  done  at  .the  bottom 
of  the  form. 

Floors,  Slabs  and  Roofs, — The  system  of  construction 
for  floors,  slabs,  and  roofs  is  determined  by  the  extent 
of  the  work  and  the  nature  of  the  loads  to  be  carried. 
If  intended  for  small  buildings  and  offices,  the  items 
can  be  made  before  erection  (Figs.  9  and  10)  ;  but  in 
the  case  of  warehouses^  factories,  piers,  and  jetties, 
where  live  loads  and  vibrator  stresses  have  to  be  borne, 
a  monolithic  structure  is  secured  by  building  in  molds 
directly  on  the  site.  For  the  lighter  classes  of  mono- 
lithic structure,  expanded  metal  is  admirably  suitable; 
it  is  also  much  used  for  the  roofs  of  reservoirs,  and  for 
thin  partitioned  walls.  The  meshing  is  simply  laid 
over  the  ribs  or  floor  beams,  which  have  been  already 
erected,  and  the  green  concrete  is  applied  to  the  acquired 
thickness,  being  supported  from  below  by  suitable  sup- 
porting work,  which  is  removed  as  soon  as  the  concrete 
has  set.  In  cold  storage  factories,  the  floor  beams  and 
ceilings  are  invariably  erected  first,  the  floor  being  laid 
afterward.  The  ceiling  is  then  solid  with  the  floor 
beams  on  their  under  side,  and  the  floor  is  solid  with 
them  on  their  upper  side,  the  air  space  between  being  a 
great  aid  to  the  maintenance  of  a  low  temperature  for 
refrigeration. 

In  the  Monier  floors  the  reinforcement  consists  of 
round  rods  varying  from  inch  to  %  inch  diameter. 
The  rods  are  spaced  at  about  six  times  their  diameter, 
and  are  crossed  at  right  angles,  being  connected  by 
iron  wire  bound  round  them.  This  artificial  method  of 
securing  the  rods  takes  considerable  time,  and  is  thus  • 
a  somewhat  costly  process.    To  produce  continuity  of 


HOW  TO  USE  THEM 


469 


metal,  the  different  lengths  of  rods  are  overlapped  for 
about  8  to  16  inches^  and  bound  with  wire. 

The  Schluter  are  similar  to  the  Monier  floors,  but 
the  rods  are  crossed  diagonally,  and  the  longitudinal 
rods  are  of  the  same  size  as  the  transverse  ones.  The 
Cottancin  floors  have  their  rods  interlaced  like  the 
canes  of  a  chair  seat  or  a  basket,  and  the  Hyatt  floors 
have  square  rods  with  holes  through  which  small  trans- 
verse rods  pass.  Over  fifty  systems  of  reinforcing  are 
in  use,  and  in  most  cases  the  only  points  of  difference 
are  the  shape  of  the  section  and  the  method  of  attach- 
ment and  adjustment. 

Beams. — It  is  obvious  that,  as  the  span  increases,  a 
limit  will  soon  be  reached  beyond  which  it  is  not  eco- 
nomical to  use  plain  floor  slabs,  far  their  dead  weight 
becomes  of  such  magnitude  as  to  prohibit  their  use.  We 
have  thus  to  resort  to  a  division  of  the  main  span  by 
cross  beams  resting  on  columns,  and  the  floor  is  laid 
on  these  beams,  which  are  arranged  to  take  as  much  of 
the  load  as  to  render  it  possible  to  reduce  the  thick- 
ness of  the  floor  within  reasonable  limits.  Reinforced 
concrete  beams  are  typical  of  the  construction  in  which 
the  merits  of  two  component  materials  are  made  to 
serve  a  common  end ;  but  in  the  particular  case  of  steel 
and  concrete,  the  actual  part  played  by  the  steel  is 
not  at  all  well  understood. 

Speaking  generally,  beams  do  not  differ  in  construe- 
tional  details  from  floors.  The  same  reinforcement  is 
used  in  both,  the  only  difference  being,  that  as  beams 
are  usually  deeper  than  floors,  the  shearing  stresses  be- 
come more  pronounced,  the  greater  provision  has  to  be 
made  for  them  by  a  liberal  use  of  stirrups  or  vertical 
binding  rods.   In  some  systems  the  reinforcement  con- 


470  CEMENTS  AND  CONCRETES 


sists  entirely  of  straight  rods,  disposed  in  any  part  of 
the  beam  where  tensile  stresses  are  likely  to  be  called 
into  play.  In  others,  specially  bent  rods  are  joined  or 
welded  to  straight  rods,  disposed  and  when  welding  has 
to  be  done  it  would  appear  that  wrought  iron  is  more 
suitable  than  steel. 

It  is  usual  to  arrange  the  dimensions  of  the  beams 
so  that  the  whole  of  the  compressive  stresses  are  taken 
by  that  portion  of  the  concrete  on  one  side  of  the  neu- 
tral axis;  but  in  some  cases,  as  with  continuous  beams 
or  heavy  beams  of  small  depth,  a  portion  of  the  rein- 
forcement is  disturbed  along  compressed  portion  of  the 
beam,  the  steel  rods  either  taking  up  the  excess  of 
compressive  stress  over  that  at  which  the  i3oncrete  can 
be  safely  worked,  or  else  taking  up  the  tensile  stresses 
at  the  places  where  they  occur  over  the  supports.  As 
a  general  rule  we  may  take  it  that  the  economical  depth 
for  a  reinforced  concrete  beam^  freely  supported  at 
both  ends,  is  one-twentieth  the  span,  and  is  thus  ap- 
proximately the  same  as  that  of  a  steel  girder  of  equal 
strength.  Reinforced  concrete  beams  are  now  made  for 
spans  up  to  100  feet  for  buildings,  and  150  feet  for 
bridges.  But  for  each  class  of  work  beyond  this  limit, 
the  weight  becomes  excessive.  Several  arched  ribs, 
for  much  greater  spans  have^  however,  been  success- 
fully built. 

The  beams  are  made  in  much  the  same  way  as  piles 
and  columns;  they  can  be  made  in  sheds  on  the  site, 
or  in  the  actual  position  they  are  to  occupy  when  fin- 
ished. The  ceiling  and  beams  are  erected  first,  the 
floor  being  afterward  worked  on  the  top  of  the  beams. 
We  thus  obtain  a  very  perfect  monolithic  structure  in 
which  any  vibration  set  up  by  machinery,  falling  loads, 


HOW  TO  USE  THEM 


471 


etc.,  will  be  of  much  less  extent  than  with  any  ordinary 
type  of  building,  in  which  there  is  often  a  great  want 
of  rigidity,  the  beams  and  arches  being  loose  and  able 
to  vibrate  independently  of  other  parts  of  the  struc«= 
ture. 

Concrete  being  as  weak  in  shear  as  in  tension,  pro- 
vision is  also  required  to  take  the  shearing  stresses. 
Some  American  designers  have  to  this  end  patented 
special  forms  of  reinforcement  bar,  in  which  each  main 
tension  bar  has  projecting  upward  from  it  ties  inclined 
at  the  angle  of  45  deg.  (Kahn  system.)  These  ex- 
tend to  the  top  of  the  bar  and  take  the  tensile  stresses 
arising  from  the  shear.  The  corresponding  compres- 
sive stress  at  right  angles  to  this  is  carried  by  the  con- 
crete. The  system  is  efficient  and  on  large  spans,  where 
weight  must  be  reduced  to  a  minimum,  it  has  its  ad- 
vantages. 

Thus,  in  the  Ransome  system  (Fig.  12),  the  shearing 
stresses  at  the  end  of  a  beam  are  taken  up  by  inclined 
reinforcing  rods  imbedded  in  the  concrete  at  the  junc- 
tion of  beam  with  column. 

Arches. — Concrete  has  long  had  an  extensive  ap- 
plication in  the  building  of  arches,  but  until  the  in- 
troduction of  reinforced  concrete  the  arches  that  could 
be  economically  and  safely  constructed  were  limited  to 
spans  of  a  few  feet.  The  general  rule  that  the  line  of 
resistance  fell  within  the  middle  third  had  to  be  ob- 
served for  simple  concrete  arches,  as  for  those  in  brick- 
work and  masonry;  and  the  thickness  of  the  arches 
at  the  crown  was  thus  approximately  the  same  whether 
built  in  either  of  these  materials.  The  introduction  of 
steel  reinforcement,  however,  made  it  possible  not  only 
to  reduce  the  thickness  of  the  ring  of  a  given  load- 


HOW  TO  USE  THEM 


carrying  capacity,  but  by  suitably  providing  for  tne 
tensile  stresses  to  enable  arches  of  much  greater  span 
and  smaller  rise  to  be  built.  Some  general  types  of 
arches  in  reinforced  concrete  are  shown  in  Figs.  13,  14, 
15  and  16.  Fig.  13  'shows  an  ordinary  arch  with  top 
and  bottom  armature.  In  many  cases  where  the  ten- 
sile stresses  can  safely  be  carried  by  the  concrete  the 
top  armature  can  be  omitted.  In  the  Melane  arches, 
shown  in  Fig.  14,  the  top  and  bottom  armatures  are 
connected  by  ligatures,  and  in  the  Hennebique  arches 
(Fig.  15)  stirrups  are  used.  As  a  general  rule,  hinges 
should  be  built  at  the  stringings  and  the  crown,  for  the 
calculations  are  much  simplified,  and  the  line  of  re- 
sistance goes  through  the  hinges;  the  arches  also  ad- 
just themselves  better  to  the  load  and  to  any  slow 
temperature  changes,  and  when  the  centering  is  struck 
the  arch  can  better  take  its  bearings  without  cracking. 
The  methods  of  calculations  for  arches  are  as  numer- 
ous as  those  for  beams,  and  generally  speaking  are  as 
irrational.  The  Monier  system  is  the  one  most  gen- 
erally adopted,  and  over  400  bridges  built  on  this  sys- 
tem now  exist  in  Europe.  In  America  expanded  metal 
and  Clinton  electrically-welded  fabric  are  often  used. 
An  example  of  the  latter  construction  will  be  found  in 
Fig.  17. 


SOME  MISCELLANEOUS  ITEMS. 


Lintels. — Concrete  lintels  and  beams  are  fast  super- 
seding those  made  of  stone  and  wood.  Lintels  are 
generally  cast  and  then  fixed. 


CEMENTS  AND  CQNCIiETES 


HOW  TO  USE  THEM 


475 


Concrete  Walls. — Many  ingenious  plans  have  been 
introduced  as  substitutes  for  wood  framing  for  retain- 
ing concrete  while  constructing  walls  and  partitions. 
The  most  simple  method  is  as  follows :  Cast  a  number 
of  concrete  angle  slabs  with  an  L  section,  and  then 
place  them  level  in  contrary  directions,  thus  [ 
spaced  to  the  width  of  the  proposed  partition  or  wall 
until  the  desired  length  of  wall  is  completed,  and  fill 
the  openings  with  rough  concrete.  When  set,  place 
another  row  on  this  (taking  care  to  break  the  joints  by 
overlapping),  and  so  on,  until  the  desired  height  is 
obtained.  Concrete  for  walls  formed  in  situ  should  be 
deposited  in  layers,  taking  care  that  each  layer  is  thor- 
oughly rammed  and  keyed,  as  described  under  the 
heading  of  ^ ^Ramming."  A  suitable  finish  for  ordi- 
nary purposes,  for  rough  walls  built  in  situ,  may  be 
obtained  by  rough  trowelling."  This  is  done  by 
first  gauging  1  part  of  Portland  cement,  1  part  of  old 
lime  putty,  and  2  parts  of  sand.  The  adding  of  lime 
renders  the  stuff  more  plastic  and  easy  to  work,  with- 
out decreasing  the  impermeability  of  the  work.  This 

limed  cement''  is  applied  with  a  hand-float,  and  is 
thoroughly  worked  into  the  crevices  of  the  concrete, 
but  leaving  no  body  on  the  surface.  The  surface  is 
then  finished  by  brushing  with  a  wet  stock-brush.  The 
walls  should  be  well  whetted  before  the  stuff  is  applied. 

Strong  Rooms. — Concrete  is  frequently  employed  in 
the  construction  of  strong-rooms  that  are  situated 
underground,  and  are  rendered  damp-proof  as  well  as 
burglar-proof,  which  is  useful  for  the  storage  of  docu- 
ments. 

Concrete  Coffins  and  Cementation. — The  great  im- 
provements in  the  manufacture  of  Portland  cement 


476  CEMENTS  AND  CONCRETES 


during  the  last  decade  has  so  cheapened  and  improved 
the  quality  as  to  bring  it  more  and  more  to  the  front 
as  one  of  the  most  useful  and  important  materials  for 
a  variety  of  purposes.  One  of  the  latest  uses  found  for 
it  is  in  the  construction  of  coffins,  by  the  author,  whose 
invented  and  registered  idea  was  that  such  a  coffin, 
made  of  specially  prepared  metallic  concrete,  would 
be  impermeable^  and  practically  indestructible,  and 
that  it  would  obviate  the  danger  of  spreading  the 
poisons  of  disease  by  preventing  the  escape  of  noxious 
gases.  The  lid  having  a  strong  piece  of  plate  glass 
embedded  in  the  concrete,  and  directly  over  the  face, 
enabled  the  mourners  to  see  the  features  of  the  depart- 
ed. The  edge  of  the  open  coffin  had  a  sunk  groove, 
and  the  lid  a  corresponding  projection,  only  smaller, 
to  allow  for  a  coat  of  fine  cement.  When  the  joints 
were  bedded  and  pressed  together  until  the  excess  ce- 
ment oozed  out,  the  coffin  was  hermetically  sealed. 
The  coffin  should  be  left  uncovered  by  cement  for 
identification,  and  so  that  friends  could  view  it  until 
the  time  of  removal  to  the  cemetery.  The  face  could 
then  be  covered  with  quick-setting  cement,  which,  join- 
ing with  the  other  portion  of  cement,  would  perma- 
nently embalm  the  body,  which  would  further  be  pro- 
tected by  fixing  the  lid  in  a  similar  way.  If  the  prop- 
erties of  this  class  of  coffin  are  taken  into  considera- 
tion, the  expense  will  be  comparatively  less  than  that  of 
wood.  If  expense  is  not  a  special  consideration,  the 
coffin  can  be  enriched  with  armorial  bearings  or  other 
devices.  The  concrete  may  also  be  polished  like  real 
granite.  One  objection  was  raised  as  to  the  weight, 
but  the  old  stone  coffms  and  those  of  oak  lined,  with 
lead  were  also  heavy.    Besides,  the  weight  would  be 


HOW  TO  USE  THEM 


477 


a  protection  against  body-snatchers,  and  bearing  in 
mind  that  a  coffin  is  only  moved  about  once  in  a  life- 
time, or  rather  at  death,  the  question  of  weight  is  un- 
important. Cementation,  from  a  sanitary  point  of 
view,  would  be  equal  if  not  superior  to  cremation.  In 
case  of  an  epidemic,  the  coffins  could  be  cemented  at 
once,  and  stacked  in  the  cemetery  until  graves  or  vaults 
were  prepared  for  them.  It  may  be  safely  said  that  it 
is  a  clean,  safe,  effectual,  rapid  and  sanitary  method 
of  disposing  of  the  dead.  If  their  manufacture  should 
not  cause  any  great  amount  of  extra  employment  for 
plasterers,  the  latter  can  at  least  make  their  own  cof- 
fins, in  frosty  weather,  when  most  works  are  stopped, 
and  they  could  use  them  as  baths  during  their  life- 
time. 

Stonette, — Stonette  is  a  composition  of  Portland  ce- 
ment and  fine  aggregate,  to  imitate  any  kind  of  stone, 
and  so  made  that  it  can  be  carved  the  same  as  natural 
stone.  The  Portland  cement  must  be  thoroughly  air< 
slaked,  finely  sifted,  and  gauged  with  the  natural  ag- 
gregate in  the  proportion  of  2  of  cement  to  7  of  ag- 
gregate. The  aggregate  is  composed  of  finely  crushed 
natural  stone,  the  same  as  that  to  be  imitated.  This 
should  be  passed  through  a  fine  sieve.  It  is  necessary, 
when  imitating  some  stones,  to  add  a  small  portion  of 
oxide  to  counteract  the  color  of  the  cement.  If  a  very 
white  stone  is  being  imitated,  the  addition  of  a  small 
proportion  of  whiting  or  French  chalk  or  well-slaked 
white  limestone,  is  necessary  to  obtain  the  desired 
color.  The  material  should  be  gauged  stiff,  and  then 
well  rammed  into  the  mould.  The  carving  is  best  done 
while  the  cast  blocks  are  green. 

Tile  Fixing. — Tile  fixing  is  in  some  places  a  sepa- 


478  CEMENTS  AND  CONCRETES 


rate  branch  of  the  building  trade^  but  it  is  generally 
recruited  from  the  ranks  of  plasterers,  and  in  some 
districts  it  is  done  by  plasterers.  As  regards  the  pro- 
cess of  placing  the  tiles,  it  is  best  to  work  from  the 
centre  of  the  space,  and  if  the  design  be  intricate,  to 
lay  out  a  portion  of  the  pavement  according  to  the 
plan,  upon  a  smooth  floor,  fitting  the  tiles  together 
as  they  are  to  be  laid.  Lines  being  stretched  over  the 
foundation  at  right  angles,  the  fixing  may  proceed, 
both  the  tiles  and  the  foundation  being  previously 
soaked  in  cold  water,  to  prevent  the  too  rapid  dry- 
ing of  the  cement,  and  to  secure  better  adhesion.  The 
border  should  be  left  until  the  last.  Its  position  and 
that  of  the  tiles  are  to  be  obtained  from  the  drawing, 
or  by  measuring  the  tiles  when  laid  loosely  upon  the 
floor.  The  cement  for  fixing  should  be  mixed  thin,  in 
small  quantities,  and  without  sand.  It  is  best  to  float 
the  tiles  to  their  places,  so  as  to  exclude  air,  and  fill 
the  spaces  between  them  and  the  foundation.  For  fix- 
ing tiles  in  grate  cheeks,  sides  and  backs  of  fire-places, 
etc.,  equal  parts  of  sand,  plaster  and  hair  mortar  may 
be  used.  These  materials  are  sometimes  mixed  with 
hot  glue  to  the  consistency  of  mortar.  The  tiles  should 
be  well  soaked  in  warm  water.  Keen's  or  other  white 
cements  are  used  as  fixing  materials  for  wall  tiles,  neat 
Portland  cement  (very  often  killed)  being  generally 
used  for  floor  work.  Tiles  may  be  cut  in  the  follow- 
ing manner :  Draw  a  line  with  a  pencil  or  sharp  point 
where  the  break  is  desired,  then  placing  the  tile  on  a 
form  board,  or  embedding  it  in  sand  on  a  flagstone, 
tap  it  moderately  with  a  sharp  chisel  and  a  hammer 
along  the  line,  up  and  down,  or  scratch  it  with  a  file. 
The  tile  may  then  be  broken  in  the  hand  by  a  gentle 


HOW  TO  USE  THEM 


479 


blow  at  the  back.  The  edges,  if  required,  may  be 
smoothed  by  grinding  or  by  rubbing  with  sand  and 
water  on  a  flat  stone.  Tiles  may  also  be  sawn  to  any 
desired  size.  Cement  should  not  be  allowed  to  harden 
upon  the  surface  of  the  tile  if  it  can  be  prevented,  as 
it  is  difficult  to  remove  it  after  it  has  set.  Stains  or 
dirt  adhering  to  tiles  may  be  removed  by  wetting  with 
diluted  muriatic  acid  (''spirits  of  salts''),  care  being 
taken  that  the  acid  is  all  wiped  off,  and,  after  wash- 
ing, the  superfluous  moisture  must  be  wiped  off  with 
a  clean,  dry  cloth.  In  order  to  obtain  a  sound  and 
straight  foundation,  which  is  imperative  for  good  per- 
manent tile  fixing,  the  substratum,  whether  on  walls  or 
floors,  should  be  composed  of  Portland  cement  gauged 
with  strong  sand  or  similar  aggregate  in  proportion 
of  1  of  the  former  to  3  of  the  latter.  The  surface  must 
be  ruled  fair  and  left  rough,  so  as  to  form  a  fair  bed 
and  key  for  the  fixing  materials  and  tiles. 

Setting  Floor  and  Wall  Tile. — As  this  work  properly 
belongs  to  the  plasterer,  where  no  regular  tile  setter  is 
available,  I  have  thought  it  proper  to  publish  the  fol- 
lowing instructions  for  doing  this  work^  which  are 
taken  from  a  treatise  prepared  for  the  Tile  Manufac- 
turers of  the  United  States.  This  treatise,  in  pamphlet 
form,  was  intended  for  distribution  among  buyers  and 
workers  in  tiles^  and  the  directions  and  suggestions 
laid  down  in  it  are  of  the  best^  and  quite  suited  to  the 
wants  of  the  workingmen : 

Foundations. — A  good  foundation  is  always  neces- 
sary, and  should  be  both  solid  and  perfectly  level.  Tile 
should  always  be  laid  upon  concrete  foundation,  pre- 
pared from  the  best  quality  of  Portland  cement  and 
clean,  sharp  sand  and  gravel,  or  other  hard  material. 


480 


CEMENTS  AND  CONCRETES 


(Cinders  sJiould  never  he  used,  as  they  have  a  tendency 
to  destroy  the  life  of  the  cement  and  cause  it  to  dis- 
integrate.) A  foundation,  however,  may  also  be  formed 
of  brick  or  hollow  tile  embedded  solidly  in  and  covered 
with  cement  mortar.  Concrete  should  be  allowed  to 
thoroughly  harden  before  laying  the  floor,  and  should 
be  well  soaked  with  water  before  laying  the  tile. 

Lime  mortar  should  never  be  mixed  with  concreting. 

Concrete  should  consist  of  one  part  Portland  cement, 
two  parts  clean  sharp  sand,  two  parts  clean  gravel, 
and  thoroughly  mixed  with  sufficient  water  to  form  a 
hard,  solid  mass  when  well  beaten  down  into  a  bed, 
which  should  be  from  inches  to  3  inches  thick.  If 
the  concrete  bed  can  be  made  over  three  inches  in 
thickness,  the  concrete  can  then  be  made  of  one  part 
Louisville  cement^  one  part  clean  sharp  sand,  one  part 
clean  gravel  and  thoroughly  mixed  with  sufficient  wa- 
ter, as  above  described. 

For  Floors. — The  surface  of  the  concrete  must  be 
level  and  finished  to  within  one  (1)  inch  of  the  fin- 
ished floor  line,  when  tile  %  inch  thick  is  used,  which 
will  leave  a  space  of  ^/^  inch  for  cement  mortar,  com- 
posed of  equal  parts  of  the  very  best  quality  Portland 
cement  and  clean  sharp  sand.  The  distance  below 
the  surface  of  the  finished  floor  line,  however,  should 
be  governed  by  the  thickness  of  the  tile. 

For  Wood  Floors. — When  tiles  are  to  be  laid  on  wood 
flooring  in  new  buildings  the  joists  should  be  set  ^ve 
inches  below  the  intended  finished  floor  line  and  spaced 
about  12  inclies  apart  and  thoroughly  bridged,  so  as  to 
make  a  stiff  floor^  and  covered  with  one-inch  boards 
not  over  six  inches  wide  (boards  three  inches  wide 
preferred),,  and  thoroughly  nailed,  and  the  joints  % 


HOW  TO  USE  THEM 


481 


inch  apart  to  allow  for  swelling.  (See  No.  31.)  (A 
layer  of  heavy  tar  paper  on  top  of  wood  flooring  will 
protect  the  boards  from  the  moisture  of  the  concrete, 
and  will  also  prevent  any  moisture  from  dripping 
through  to  a  ceiling  below.) 


Pig-.  31. 


In  Old  Buildings. — ^Cleats  are  nailed  to  joists  five 
inches  below  the  intended  finished  floor  line,  and  short 
pieces  of  boards  %  inch  apart  fitted  in  between  the 

FLOOR  LlMg 


IFLOOR 


Pig-.  32. 

joists  upon  the  cleats  and  well  nailed,  and  the  joists 
thorough^  bridged.  The  corners  on  the  upper  edge 
of  the  joists  should  be  chamfered  off  to  a  sharp  point 
(see  Fig.  32),  as  the  flat  surface  of  the  joists  will  give 
an  uneven  foundation.  AVhen  the  strength  of  the 
joists  will  permit,  it  is  best  to  cut  an  inch  or  more  off 


482  CEMENTS  AND  CONCEETES 


the  top.  (Where  joists  are  too  weak,  strengthen  by 
thoroughly  nailing  cleats  six  inches  wide  full  length 
of  joists.)  When  the  solid  wood  foundation  is  thus 
pref)ared,  concrete  is  placed  upon  it  as  above  directed. 

Where  Steel  Beams  and  hollow  tile  arches  are  used, 
frequently  very  little  space  is  left  for  preparing  a 
proper  foundation  for  setting  tile,  as  the  rough  coating 
is  usually  put  in  by  the  hollow  tile  contractor  to  pro- 
tect his  work,  but  this  covering  should  always  conform 


Fig.  33. 


to  the  requirements  for  a  solid  tile  foundation.  Should 
this  not  be  the  case,  the  tile  contractor  should  remove 
sufficient  of  the  covering  to  allow  him  to  put  down  a 
foundation  that  will  insure  a  satisfactory  tile  floor. 
(Cinders,  lime,  mortar  or  inferior  material  must  never 
be  used.) 

The  tops  of  iron  beams  should  be  from  three  to  four 
inches  below  che  finished  floor  line,  to  prevent  floors, 
when  finished,  showing  lines  of  the  beams. 

For  Hearths. — The  foundation  for  hearths  should  be 
placed  upon  a  brick  arch,  if  possible,  to  ensure  perfect 
fire  protection,  and  then  covered  with  concrete  in  the 
same  manner  as  directed  for  tile  floors.  If  placed 
upon  a  sub-foundation  of  wood,  the  concreting  should 
be  at  least  six  inches  thick.    (See  Figs.  34  and  35.) 


HOW  TO  USE  THEM 


483 


484  CEMENTS  AND  CONCRETES 


For  Wa/^^.— When  tiles  are  to  be  laid  on  old  brick 
walls  the  plaster  must  be  all  removed  and  the  mortar 
raked  out  of  the  joints  of  the  brick  work  to  form  a  key 
for  the  cement.  On  new  brick  walls  the  points  should 
not  be  pointed.  When  tiles  are  to  be  placed  on  stud- 
ding, the  studding-  should  be  well  braced  by  filling 
in  between  the  studding  with  brick  set  in  mortar  to  the 
height  of  tile  work  (see  Fig.  36)  ;  or  brick  work  may  be 
omitted  and  extra  studding  put  in  and  thoroughly 


bridged,  so  as  to  have  as  little  spring  as  possible,  and 
this  studding  then  covered  with  sheet  metal  lathing. 
(See  Fig.  37.)  {Tile  must  never  he  placed  on  wood  lath 
or  on  old  plaster,)  The  brick  walls  must  be  well  wet 
with  water  and  then  covered  with  a  rough  coating 
of  cement  mortar,  composed  of  one  part  Portland  ce- 


HOW  TO  USE  THEM  485 

ment  and  two  parts  clean  sharp  sand.  When  tiles  are 
placed  on  metal  lathing,  hair  should  be  mixed  with  the 
cement  mortar  to  make  it  adhere  more  closely  to  the 
lath.  The  cement  mortar  should  be  %  inch  thick,  or 
sufficient  to  make  an  even  and  true  surface  to  within 
one  (1)  inch  of  the  intended  finished  surface  of  the 
tile,  when  tile      inch  thick  is  used,  which  will  allow 


a- space  of  %  inch  for  the  cement  mortar,  composed  as 
above  for  rough  coating  the  walls.  The  face  of  the 
cement  foundation  should  be  roughly  scratched  and 
allowed  to  harden  for  at  least  one  day  before  com- 
mencing to  lay  the  tile.  -  If  any  lime  is  mixed  with  the 
cement  mortar  for  setting  the  tiles^  it  should  never 
exceed  10  per  cent.,  and  great  care  must  be  used  to 
have  the'  lime  well  slaked^  and  made  free  from  all 


486 


CEMENTS  AND  CONCRETES 


lumps  by  running  through  a  coarse  sieve,  in  order  to 
guard  against  heaving"  or  swelling,"  and  thus 
loosening  or  ^ lifting"  the  tiles. 

Important, — The  foundation  for  both  floor  and  wall 
tiling  should  be  thoroughly  brushed,  to  remove  all  dust 
and  small  particles  adhering  to  it,  and  then  well  wet 
before  putting  on  the  cement  mortar.  To  ensure  a 
perfect  bond  it  is  best  to  coat  the  foundation  by  brush- 
ing over  it  pure  cement  mixed  in  water. 

Cement. — The  very  best  quality  of  Portland  cement 
should  always  be  used  for  setting  either  floor  or  wall 
tile  and  for  grouting  the  floors,  and  the  very  best 
quality  of  Keene's  Imported  Cement  for  filling  the 
joints  in  the  wall  tiling. 

Sand. — Clean,  sharp  grit  sand,  free  from  all  salt, 
loam  or  other  matter,  and  perfectly  screened  before 
mixing  with  the  cement,  should  always  be  used. 

Mortar. — For  floors  or  vitrecus  tiles,  should  be  com- 
posed of  equal  parts  of  cement  and  sand,  and  for  wall 
tiles  one  (1)  part  of  cement  and  two  (2)  parts  sand. 
The  mortar  should  not  be  too  wet,  but  should  be  rather 
stiff,  and  should  always  be  used  fresh,  as  mortar,  when 
allowed  to  set  before  using,  loses  a  portion  of  its 
strength. 

Soaking, — Tiles  must  always  be  thoroughly  soaked 
in  water  before  setting,,  which  makes  the  cement  unite 
to  the  tiles. 

The  Tiles  for  the  Floors  are  first  laid  out  to  ascer- 
tain if  they  are  all  right  and  compared  with  the  plan 
provided  for  laying  the  floors.  Strips  are  then  set, 
beginning  at  one  end  of  and  in  the  centre  of  the  room, 
and  level  with  the  intended  finished  floor  line.  Two 
sets  of  guide  strips  running  parallel  about  18  to  30 


HOW  TO  USE  THEM 


487 


inches  apart  should  be  set  first.  (See  Pig.  38.)  The 
mortar  is  then  spread  between  them  for  about  six  to 
ten  feet  at  a  time,  and  level  with  a  screed  notched  at 
each  end^  to  allow  for  the  thickness  of  the  tiles.  The 
tiles  are  placed  upon  the  mortar,  which  must  be  stiff 
enough  to  prevent  the  mortar  from  working  up  be- 


Y   /   .    V  V 

<         X  X 
r  V      r  V 

1 

1  1 

H  • 
'l  1 

t  1 

V  Y 
«  t 

V  y 

X  A 

i 

i 

\X  X 

i\  I  r 
1  >  1 

X  >i ! 

! 

--.      >  ■ 

»  1 

c  -\  >' 

V     >  '  > 

'    N  '     N'     >-.-•'              .1  •      r  •  • 

Fig.  38. 


tween  the  joints.  The  tiles  are  to  be  firmly  pressed 
into  the  mortar  and  tamped  down  with  a  block  and 
hammer  until  they  are  exactly  level  with  the  strips. 
When  the  space  between  the  strips  is  completed,  the 
strips  on  one  side  of  the  tile  is  moved  out  18  to  30 
inches  and  placed  in  proper  position  for  laying  an- 
other section  of  tile,  using  the  tiles  which  have  been 


488  CEMENTS  AND  CONCRETES 


laid  for  one  end  of  the  screed^  and  the  laying  of  the 
tile  continued  in  the  same  manner  until  the  floor  is 
, finished.  When  the  cement  is  sufficiently  set^  which 
should  be  in  about  two  days,  the  floor  should  be  well 
scrubbed  with  clean  water  and  a  broom,  and  the  joints 
thoroughly  grouted  with  pure  cement  (mixed  with 
water  to  the  consistency  of  cream).  As  soon  as  this 
begins  to  stiffen,  it  must  be  carefully  rubbed  off  with 
sawdust  or  flne  shavings  and  the  floor  left  perfectly 
clean. 

Ceramics, — The  foundation  and  cement  mortar  for 
ceramics  are  the  same  as  for  plain  or  vitreous  floors, 
and  the  guide  strips  used  in  the  same  manner.  Tlu 
cement  mortar  is  then  spread  evenly  and  the  tile  sheets 
laid  carefully  on  it  with  the  paper  side  up.  After  the 
batch  is  covered,  the  tile  setter  should  commence  to 
press  the  tile  into  the  mortar,  gently  at  first,  firmly 
afterwards,  using  block  and  hammer,  thus  leveling 
the  tile  as  correctly  as  possible.  The  tile  should  be 
beaten  down  until  the  mortar  is  visible  in  the  joints 
through  the  paper ;  however,  without  breaking  it.  The 
pa])er  is  then  moistened,  and  after  it  is  well  soaked 
and  can  be  easily  removed,  it  is  pulled  off  backwards, 
starting  from  a  corner.  After  removing  the  paper,  the 
tile  should  be  sprinkled  with  white  sand  before  fin- 
ishing the  beating,  so  that  the  tiles  will  not  adhere  to 
the  beater,  owing  to  the  paste  which  is  used  in  mount- 
ing them.  Corrections  of  the  surface  are  then  made 
by  leveling  it  with  block  and  hammer.  The  filling  of 
the  joints  and  cleaning  of  the  surface  is  a  delicate  op- 
eration, as  the  looks  of  this  work  depends  largely  upon 
it.  The  joints  are  to  be  filled  with  clean  Portland 
ceraent  mixed  with  water.    This  mixture  is  forced  into 


HOW  TO  USE  THEM  489 


the  joints  with  a  flat  trowel  (not  with  a  broom,  which 
often  scrapes  out  the  joints).    After  the  joints  are 


SCRtBQ 


^concrete: 
Fig.  39. 


fiHed,  the  surplus  cement  is  removed  from  the  sur- 
face by  drawing  a  wet  piece  of  canton  flannel  over  it. 


Fig.  40. 


This  piece  of  cloth  must  be  washed  out  frequently  with 
clean  Avater.    After  the  floor  is  cleaned,  it  should  be. 


490  CEMENTS  AND  CONCRETES 


allowed  to  stand  for  a  day  or  two^  when  the  whole 
floor  is  to  be  rubbed  with  sharp  sand  and  a  board  of 
soft  lumber.  This  treatment,  which  the  last  traces  of 
cement,  is  preferable  to  the  washing  off  with  an  acid 
solution,  as  it  will  not  attack  the  cement  in  the  joints. 
In  laying  the  tile  sheets  on  the  cement,  care  should  be 
taken  to  have  the  widths  of  joints  spaced  the  same  as 
the  tile  on  the  sheets  to  prevent  the  floor  having  a  block 
appearance. 


Fig.  41. 


The  Tiles  for  the  Walls  or  Wainscoting  are  first  laid 
out  and  compared  with  the  plan  provided  for  setting 
them.  Guide  strips  are  then  placed  on  the  wall  paral- 
lel and  about  two  feet  apart,  the  bottom  one  being  so 


HOW  TO  USE  THEM 


491 


arranged  as  to  allow  the  base  to  be  set  after  the  body 
is  in  place.  (See  Fig.  40.)  When  "a  cove  base  is  used 
it  ma}^  be  necessary  to  set  it  firsts  but  in  all  cases  must 
be  well  supported  on  the  concrete.  (See  Fig.  41.)  The 
strips  must  be  placed  plumb  and  even  with  the  intend- 
ed finished  wall  line.  The  method  of  setting  wall  tile 
is  governed  to  some  extent  by  the  conditions  of  the 
wall  on  which  they  are  to  be  set^  and  must  be  decided 
by  the  mechanic  at  the  time,  which  process  he  will 
use,  whether  buttering  or  floating,  as  equally  good 
work  can  be  done  by  either,  by  following  the  instruc- 
tions, as  stated  below. 

Floating  Wall  Tile. — The  mortar  is  spread  between 
the  guide  strips  for  about  five  feet  at  a  time  and  lev- 
elled with  a  screed  notched  at  each  end  to  allow  for 
the  thickness  of  the  tile.  (See  Fig.  39.)  The  tiles  are 
placed  in  position  and  tamped  until  they  are  firmly 
united  to  the  cement  and  level  with  the  strips.  When 
the  space  between  the  strips  is  completed,  which  should 
be  one  side  of  the  room,  the  strips  are  removed  and 
the  work  continued  in  the  same  manner  until  com- 
pleted. When  the  tiles  are  all  set,  the  joints  must  be 
carefully  washed  out  and  neatly  filled  with  thinly 
mixed  pure  Keene's  Cement,  and  all  cement  remaining 
on  the  tile  carefully  wiped  off. 

Buttering  Wall  Tiles.\i — The  cement  mortar  is  spread 
on  the  back  of  each  tile,  and  the  tile  placed  on  the 
wall,  and  tapped  gently  until  firmly  united  to  the  wall 
and  plumb  with  the  guide  strips.  When  the  tiles  are 
all  set,  the  joints  must  be  carefully  washed  out  and 
filled  with  Keene's  Cement,  and  the  tiles  cleaned  as 
directed  above. 

When  fixtures  of  any  kind  are  to  be  placed  on  the 


492  CEMENTS  AND  CONCRETES 


tile  work^  such  as  plumbing  in  bathroom,  provision 
should  be  made  for  them  by  fastening  wood  strips  on 
the  wall  before  the  rough  or  first  coating  of  cement 
mortar  is  put  on,  the  strips  to  be  the  same  thickness 
as  the  rough  coating.  The  tiles  can  be  placed  over 
the  strips  by  covering  them  with  cement  mortar,  and 
when  thoroughly  set,  holes  can  be  bored  in  the  tiles  for 
fastening  the  fixtures  without  injuring  the  tiling. 

Hearth  and  Facing  Tile  are  set  in  the  same  manner 
as  for  floors  and  walls. 

Cleaning. — It  is  absolutely  necessary  to  remove  with 
sawdust,  and  afterwards  with  a  flannel  cloth  and  wa- 
ter, all  traces  of  cement  which  may  have  been  left  on 
the  surface  of  the  tile,  as  it  is  hard  to  remove  after  it 
is  set. 

After  thoroughly  cleaning  the  fioor^  it  should  be 
covered  with  sawdust  and  boards  placed  on  the  floor 
for  several  days  where  there  is  walking  upon  it. 

A  w^hite  scum  sometimes  appears  on  the  surface  of 
the  tile,  caused  by  the  cement.  This  can  generally  be 
removed  by  washing  frequently  with  plenty  of  soap 
and  water.  If  this  does  not  remove  it,  then  use  a  weak 
solution  of  15  parts  muriatic  acid  and  85  parts  wa- 
ter, which  should  only  be  allowed  to  remain  on  the 
tile  for  a  few  minutes,  and  then  thoroughly  washed 
off. 

Cutting  of  Tile. — When  it  is  found  necessary  to  cut 
tile  the  following  directions  are  given : 

TooZ5.i/— The  chisels  used  should  be  made  of  the  best 
tool  steel,  and  should  always  be  sharp.  They  should 
be  of  small  size,  the  edge  not  being  wider  than  one- 
fourth  inch.  The  hammer  should  be  light,  weighing 
about  six  ounces,  having  a  slender  handle.    After  the 


HOW  TO  USE  THEM 


493 


exact  shape  of  the  tile  has  been  determined,  lines 
should  be  drawn  on  the  surface  of  the  tile  with  a  lead 
pencil,  giving  the  exact  direction  of  the  cut  desired. 
This  line  should  be  folloAved  with  the  chisel,  which  is 
held  at  right  angles  with  the  surface,  the  hammer 
giving  the  chisel  sharp^  decisive  raps.  After  the  line 
has  been  repeatedly  traversed  with  the  chisel,  a  few 
sharp  blows  against  the  back  of  the  tile  opposite  the 
mark  on  the  face  will  break  it  at  the  place  thus 
marked. 

To  cut  glazed  or  enamel  tiles,  they  should  be 
scratched  on  the  surface  with  a  tool  at  the  place  where 
it  is  desired  to  break  them,  and  then  gently  tapped 
on  the  back  opposite  the  scratch. 

Caution  should  be  used  not  to  allow  any  one  to 
walk  upon  or  carry  anything  heavy  over  the  floor,  or 
have  any  pounding  about  wall  work  for  several  days, 
or  until  the  tiles  are  flrmly  set.  Unless  these  precau- 
tions are  taken  it  will  be  impossible  to  guarantee  a 
first-class  job.  Tile  work  is  frequently  condemned 
when  the  fault  lies  with  the  rush  of  other  contractors  to 
finish  their  work. 

Laying  Tile  on  Wood. — A  new  material  called 
''Monolith/'  manufactured  by  The  Wisconsin  Mantel 
&  Tile  Co.,  that  enables  the  workman  to  lay  tiles  on 
a  wooden  floor.  There  are  many  places  where  tile 
could  be  used,  but  on  account  of  the  added  weight  to 
the  floor  by  the  use  of  cement,  concrete  foundation,  it 
is  impracticable  to  lay  in  many  places,  but  by  the  use 
of  Monolith,  the  only  weight  that  is  added  is  the  tile 
itself  and  the  Monolith  bed  it  is  laid  in.  Both  ma- 
terials are  only  five-eighths  of  an  inch  in  thickness 
when  laid. 


CEMENTS  AND  CONCRETES 


HOW  TO  USE  THEM  495 

The  illustration,  Fig.  42,  shows  the  method  of  laying 
the  tile.  The  paper  to  which  the  small  pieces  of  tiles 
are  glued  is  seen  on  top  of  tiles.  The  dark  part  shows 
the  patent  cement,  or  Monolith. 

I  show  herewith^  at  Nos.  43  and  44,  twelve  designs 
for  decorative  borders  of  various  kinds,  and  in  45 
and  46  I  show  two  designs  well  suited  for  vestibules, 
store  entrances  or  for  hearths  in  fire-places. 

Good  Concrete. — In  determining  the  proportions  of 
the  aggregates  and  cement  for  a  certain  piece  of  work, 
it  is  necessary  usually  to  take  samples  of  the  broken 
stone  (or  gravel)  and  sand  which  are  most  available 
to  the  site  and  make  measuren;ients  of  the  percentage 
of  voids  in  the  stone  w^hich  must  be  filled  by  the  sand 
and  the  percentage  of  voids  in  the  sand  which  must 
be  filled  by  the  cement.  This  is  done  by  taking  a 
cubic  foot  box  and  filling  it  with  broken  stone  in  a 
thoroughly  wet  state.  The  box  is  then  filled  with  as 
much  water  as  is  required  to  completely  fill  it,  in  addi- 
tion to  the  stone,  which  upon  being  poured  off  gives 
the  relation  between  the  volume  of  the  voids  and  the 
volume  of  the  stone.  The  required  amount  of  local 
sand  thus  determined  is  then  measured  out  and  placed 
in  the  box  with  the  stone  in  a  damp  state.  Water  is 
then  used  to  determine  the  percentage  of  voids  left  in 
the  sand,  which  gives  the  approximate  amount  of 
cement  required,  although  an  excess  of  cement  is  al- 
most invariably  used.  Engineers  everywhere  differ 
regarding  the  best  proportion  to  be  used,  but  in  gen- 
eral the  above  test^  roughly  made,  will  determine  it 
well  enough.  The  proportions  which  are  most  univer- 
sally used  are  as  follows:  1  cement,  2  sand,  4  broken 
stone;  where  extremely  strong  work  is  desired.  Tests 


496 


CEMENTS  AND  CONCRETES 


BoROEft  No.  413 


>•  .      .      .  'VA .  •••••  ^      ,  A*  .  ••••••  ^  A/^i 

^^^^^^^^^^^^ 


Fi^.  43. 


HOW  TO  USE  THEM 


497 


Fig-.  44, 


498  CEMENTS  AND  CONCEETES 


show  that  a  6-inch  thickness  of  1-2-4  concrete  properly 
made  is  waterproof  up  to  about  50  pounds  to  the  square 
inch.  This  concrete  is  frequently  used  for  facing 
dams.  1-3-6  is  the  proportion  generally  used  for  the 
interior  of  dams  and  large  structures.  It  is  entirely 
suitable  for  large  foundations.  1-4-8  is  frequently 
used  for  foundation  work^  and  when  properly  mixed 


Fig.  45. 


makes  good  concrete,  although  it  is  about  the  limit 
of  what  is  considered  good  work,  and  would  not  be 
suitable  for  very  important  structures.  1-5-10  is  equal 
to  any  concrete  made  with  natural  cement.  It  is  a 
well-known  fact  that  the  volume  of  concrete  when 
mixed  with  water  is  somewhat  less  than  the  volume  of 
the  aggregate  and  cement  before  mixing.  The  con- 
tractors' rule  is  that  the  volume  of  mixed  concrete  is 


HOW  TO  USE  THEM 


499 


equal  to  the  volume  of  the  stone  plus  one-half  to  one- 
third  the  volume  of  sand. 

There  has  been  much  discussion  among  engineers 
and  others  as  to  the  amount  of  water  that  should  be 
added  to  the  aggregates  and  cement  for  making  the 
best  concrete,  and  while  it  is  not  the  purpose  of  this 
paper  to  enter  into  this  controversy,  it  might  be  said 
that  the  modern  tendency  is  toward  wet  concrete.  The 
old  way  was  to  add  just  enough  water  so  that  when  all 


Fig.  46. 


the  concrete  was  in  the  form  and  tamped,  it  would 
^how  moisture  on  the  surface.  The  tamping  is  a  very 
important  part  of  the  operation,  and  the  quality  of 
the  work  is  dependent  upon  how  well  this  is  super- 
intended, as  unless  it  is  well  and  thoroughly  done  the 
concrete  is  liable  to  be  honeycombed  and  imperfect, 
especially  near  the  forms.    With  the  growth  of  the 


500  CEMENTS  AND  CONCRETES 


use  of  concrete  the  old  method  of  putting  it  in  the 
forms  nearly  dry  and  depending  on  tamping  to  con- 
solidate  it  has  been  more  or  less  abandoned,  and  the 
more  modern  way  is  to  put  the  concrete  in  quite  wet, 
as  less  tamping  is  required  and  much  labor  and  ex- 
pense saved.  One  of  the  great  objections  to  this 
scheme  is  that  if  care  is  not  taken  the  water  will  tend 
to  wash  the  cement  from  the  stone  and  sand;  in  other 
words,  unmix  it.  However,  it  may  be  said  that  it 
is  now  generally  understood  that  rather  wet  concrete 
properly  handled  makes  better  work.  The  amount  of 
water  to  be  added  to  the  aggregates  and  cement  va- 
ries from  1  water  to  3  cement  by  measurement  to  12 
per  cent  of  water  by  weight.  Mr.  Carey,  of  New- 
haven,  England,  says  that  23  gallons  water  per  cubic 
yard  of  cement  was  the  best  mixture.  Quite  frequent- 
ly salt  water  is  used  in  mixing  concrete  in  cold  weather 
to  prevent  freezing,  and  it  seems  to  have  no  ill  effects 
on  the  resulting  mixture. 

Reinforced  Concrete, — Up  to  the  last  few  years  the 
use  of  concrete  as  a  building  material  was  chiefly  con- 
fined to  the  construction  of  foundations,  piers,  reser- 
voir dams  and  similar  purposes,  in  which  the  stresses 
to  be  met  Avere  almost  entirely  simple  pressures.  In- 
deed, even  fifteen  years  ago,  many  engineers  looked 
askance  on  the  use  of  concrete  for  arches,  considering 
it  for  this  purpose  much  inferior  to  brick.  Much  of 
the  caution  shown  in  extending  the  use  of  this  valua- 
ble material  doubtless  arose  from  the  frequency  with 
which  concrete  masonry  exhibited  unsightly  cracks, 
due  largely  to  the  material  being  allowed  to  get  too 
dry  while  hardening.  At  the  same  time,  careful  ex- 
amination has  shown  that  cracks  of  the  same  char- 


HOW  TO  USE  THEM 


501 


acter  are  common  in  masonry  of  all  kinds,  but  are 
unnoticed,  because  they  follow  the  regular  joints  of 
the  structure ;  whereas,  on  the  smooth  uniform  sur- 
face of  the  concrete,  cracks  of  much  less  significance 
are  immediately  visible. 

The  plan  of  reinforcing  the  material  with  metal,  of 
which  several  systems  have  been  introduced  during 
the  last  four  years,  has  greatly  extended  the  possible 
use  of  concrete ;  and  it  appears  that  in  many  cases  a 
reinforced  concrete  bridge  may  compete,  even  in  first 
cost,  with  a  steel  girder;  while  as  regards  upkeep,  it 
has,  of  course,  many  advantages.  Small  bridge  cul- 
verts of  this  material  were  extensively  used  by  Rus- 
sian engineers  in  building  the  Manchurian  Railway. 
For  openings  of  some  7-foot  span,  fiat  slabs  of  con- 
crete reinforced  with  rails  were  used,  the  thickness 
being  8%  inches.  A  similar  system  was  used  for  spans 
up  to  21  feet,  the  concrete,  however,  being  thickened 
at  the  center  as  the  span  increased,  the  depth  at  this 
point  being  2  feet  6^  inches  for  the  21-foot  span,  and 
proportionately  less  for  smaller  openings.  The  thick- 
ness at  the  bearings  was,  however,  the  same  in  all 
cases,  viz.,  8Vt  inches.  The  line  was  thrown  over  the 
spans  as  little  as  seven  days  after  completion.  The 
concrete  consisted  of  one  part  cement,  two  sand  and 
five  broken  stone.  The  system  in  this  case  had  great 
advantages,  as  stone  for  masonry  was  unobtainable, 
and  could,  moreover,  only  be  used  for  arches,  which 
would  have  necessitated  the  use  of  higher  embank- 
ments than  were  required  with  the  ferro-concrete,  used 
as  described.  Much  larger  spans  have,  of  course,  been 
built  than  those  mentioned.  One,  of  153-foot  span, 
carrying  four  main  line  tracks,  has  recently  been 


502 


CEMENTS  AND  CONCRETES 


built  for  the  Lake  Shore  and  Michigan  Southern  Rail- 
road, while  Mr.  Edwin  Thacker,  M.  Am.  Soc.  C.  E., 
states  he  considers  the  system  feasible  for  spans  up 
to  500  feet,  and  has  actually  got  out  designs  for  a 
span  300  feet,  the  cost  comparing  favorably  with  that 
of  a  steel  bridge. 

One  great  drawback  to  the  extension  of  the  system 
lies  in  the  difficulty  in  proportioning  structures  thus 
built  in  a  thoroughly  rational  manner.  In  the  case  of 
steel  bridges  certain  simple  assumptions  as  to  the 
elasticity  and  strength  of  the  material  suffice.  These 
assumptions  are  doubtless  not  absolutely  exact,  but  are 
sufficiently  near  the  truth  for  practical  purposes.  The 
elastic  properties  of  concrete  are,  however,  very  dif- 
ferent from  those  of  steel;  Hooke's  law  is  not  even  ap- 
proximately correct,  and,  moreover,  the  material  al- 
ways takes  a  permanent  set  when  first  loaded.  The 
true  distribution  of  the  stress  and  strain  on  a  concrete 
beam  is  thus  a  much  more  complicated  matter  than  it  is 
in  the  case  of  a  steel  joist,,  in  which  it  is  permissible, 
within  working  limits  of  stress,  to  assume  the  accuracy 
of  Hooke's  law.  The  assumption  generally  made  in 
the  case  of  ferro-concrete  is  that  plane  sections  of  a 
concrete  beam  remain  plane  after  bending.  This  pos- 
tulate is,  of  course,  that  commonly  made  in  propor- 
tioning steel  work ;  and  in  the  latter  case,  stress  being 
proportional  to  strain,  the  usual  formula  for  the  work- 
ing strength  of  beams  is  readily  reduced.  In  the  case 
of  concrete,  however,  the  stress-strain  curve  is  much 
more  complex.  Nevertheless,  M.  Considere  has  shown 
that  by  making  experiments  on  concrete  in  simple  ten- 
sion and  compression,  and  plotting  the  corresponding 
stress-strain  curves,  it  is  possible  to  deduce  from  these 


HOW  TO  USE  THEM 


503 


with  fair  accuracy  the  load-deflection  curve  of  a  ferro- 
concrete beam. 

This  method,  though  logical,  leads,  however,  to  no 
simple  formula  for  the  strength;  and  in  applying  this 
method  the  working  load  of  any  particular  concrete 
beam  would  have  to  be  deduced  by  the  tedious  proc- 
ess of  scaling  off  the  stress-strain  curves  at  a  num- 
ber of  points,  and  combining  the  results.  A  further 
question  arises  as  to  whether  this  stress-strain  curve 
should  be  the  initial  stress-strain  of  the  concrete,  or 
that  obtained  after  repeated  loadings.  Probably  the 
latter  is  the  best  to  choose,  but  in  that  case  it  by  no 
means  follows  that  the  metal  reinforcement  is  free 
from  initial  stresses  when  the  load  is  applied  to  the 
beam ;  and  if  the  metal  is  subject  to  initial  stress,  it  is 
obvious  that  similar  ones  must  exist  in  the  concrete. 
In  fact,  M.  Considere  has  shown  that  this  is  necessarily 
the  case  in  any  circumstances,  since,  if  the  concrete  is 
allowed  to  harden  under  water,  it  tends  to  expand, 
*  and  this  expansion  is  resisted  by  the  metal  reinforce- 
ment. If,  on  the  other  hand,  the  hardening  takes 
place  in  air  the  concrete  tends  to  contract;  and  this 
contraction  being  again  resisted  by  the  metal,  a  series 
of  fine  hair  cracks  are  produced  which,  visible  at  low 
loads,  are  readily  detected  on  the  tension  side  of  a 
heavily  loaded  ferro-concrete  beam. 

In  view  of  the  uncertainties  introduced  by  the  dif- 
ferent factors  above  mentioned,  it  is  really  questionable 
whether,  after  all^  the  theoretically  objectionable  for- 
mula of  M.  Hennebique  is  not  as  good  as  any  other. 
The  latter  all  involve  a  preliminary  calculation  of  the 
position  of  the  neutral  axis,  which  varies  with  the  per- 
centage of  metal  used^  and  with  the  type  of  stress- 


504 


CEMENTS  AND  CONCRETES 


strain  curve  assumed  for  the  concrete ;  and  also  with 
the  maximum  stress  at  any  particular  section.  Thus, 
in  a  centrally-loaded  beam,  its  position  at  the  ends  is 
entirely  different  from  what  it  is  at  the  centre.  M 
Hennebique,  on  the  other  hand^  makes  no  attempt  tc 
locate  this  neutral  axis,  and  simply  assumes  that  one- 
half  of  his  beam  resists  compression,  and  that  the 
stress  is  uniformly  distributed  over  this  half.  The 
moment  of  this  compression  about  the  centre  of  the 
section  equates  to  half  the  moment  due  to  the  load, 
and  the  other  half  of  the  moment  due  to  the  load  he 
equates  to  the  moment  about  the  centre  of  the  section 
of  the  tensile  stress  on  the  metal  reinforcement.  The 
working  strength  of  concrete  in  compression,  he  takes 
as  350  pounds  per  square  inch,  and  neglects  entirely  its 
strength  in  tension.  The  working  tensile  stress  on  the 
steel  reinforcement  he  takes  as  14,000  pounds  per 
square  inch.  This  method  is,  of  course,  totally  illogi- 
cal, yet  many  thousand  cubic  yards  of  ferro-concrete 
have  been  successfully  designed  on  these  lines;  and  a 
comparison  of  the  strength  of  ferro-concrete  beams 
as  calculated  by  this  formula,  and  by  those  of  a  more 
rational  type,  shows  very  little  difference  between  the 
two  for  a  considerable  range  of  metal  to  concrete.  On 
the  other  hand,  it  must  not  be  forgotten  that  formulae 
which  are  non-rational  in  form  are  always  risky  when 
applied  to  extreme  conditions. 

Concrete  being  as  weak  in  shear  as  in  tension,  pro- 
vision is  also  required  to  take  the  shearing  stresses. 
Some  American  designers  have  to  this  end  patented 
special  forms  of  reinforcement  bar,  in  which  each  main 
tension  bar  has  projecting  upward  from  the  ties  in- 
clined at  an  angle  of  45  degrees.    These  extend  to  the 


HOW  TO  USE  THEM 


505 


top  of  the  bar  and  take  the  tensile  stresses  arising 
from  the  shear.  The  corresponding  compressive  stress 
at  right  angles  to  this  is  carried  by  the  concrete.  The 
system  is  doubtless  efficient^  and  on  large  spans,  where 
weight  must  be  reduced  to  a  minimum  it  may  have 
some  advantage;  but  in  work  of  ordinary  proportions 
it  seems  to  be  little  superior  to  the  Hennebique  sys- 
tem, in  which  the  necessary  strengthening  is  provid- 
ed by  stirrups  of  flat  iron  bent  into  a  U  shape.  The 
main  reinforcing  bars  rest  in  these  stirrups  at  the 
lower  ends.  The  spacing  of  the  stirrups  depends  upon 
the  'Sveb  stresses''  to  be  taken,  which  can  easily  be 
calculated  by  assuming  the  reinforced  beam  to  be  a 
latticed  girder,  the  lower  chord  of  which  is  represented 
by  the  metal  reinforcement,  the  upper  one  by  the  centre 
of  the  compression  half  of  the  beam,  while  the  stirrups 
represent  vertical  ties,  which  may  be  taken  as  con- 
nected together  at  top  and  bottom  by  inclined  imag- 
inary struts.  The  advantage  of  this  simple  method  of 
reinforcing  for  shear  lies  in  the  possibility  of  using 
common  rolled  sections  for  the  whole  of  the  rein- 
forcement. 

M.  Hennebique  constructs  most  of  his  ferro-concrete 
work  on  the  monolithic  system,  girders,  piers,  columns 
and  floors  being  solidly  connected  together.  It  is, 
therefore,  necessary  to  provide  for  the  reversed  bend- 
ing moments  over  the  point  of  support,  which  is  done 
by  bending  up  half  of  the  total  reinforcement  bars, 
so  that  the  ends  of  the  span  are  close  to  the  upper 
surface  of  the  beam,  and  thus  in  a  position  to  take 
the  heavy  tensile  stresses  which  ensue  at  these  points 
when  the  monolithic  system  of  construction  is  fol- 
lowed.   The  exact  calculation  of  the  reactions  and 


506  CEMENTS  AND  CONCRETES 


bending  moments  here  is  impracticable,  if  not  actually 
impossible;  and  those  engineers  who  attach  much  im- 
portance to  having  all  structures  statically  determinate 
will  doubtless  object  to  the  plan,  but  experience  shows 
that  the  advantages  gained  are  very  considerable.  The 
structure  then  resists  as  a  unit;,  and  in  particular  its 
rigidity  is  marvelous. 

Some  comparative  tests  on  this  point,  made  by  the 
Railway  Company,  showed  that  with  a  ferro-concrete 
floor  subjected  to  blows  four  times  as  heavy  as  were 
applied  to  an  equivalent  floor  constructed  of  brick 
arches  on  steel  joists,  the  deflection  was  only  one- 
seventh  as  great. 

The  extreme  rigidity  attainable  with  the  monolithic 
system  of  construction  was  also  very  evident  in  the 
case  of  the  large  Hennebique  bridge  at  Purfleet.  Since 
a  structure  fails  by  strain  rather  than  by  stress,  the 
small  deformation  noted  with  ferro-concrete  are  evi- 
dent that  as  an  average  the  material  is  relatively  lit- 
tle tried  by  the  loads  carried.  It  must,  however,  be 
admitted  that  this  low  average  strain  is  quite  com- 
patible with  extremely  severe  strain  at  particular 
points ;  but  it  is,  of  course,  the  business  of  the  designer, 
by  suitably  disposing  his  material  to  avoid  these  pos- 
sible local  abnormalities. 

Occasionally,  doubts  have  been  expressed  as  to 
Avhether  the  metallic  reinforcement  may  not  suffer  from 
corrosion  as  time  goes  on.  This  would  be  extremely 
dangerous  if  it  occurred,  since  the  metal  being  out  of 
sight,  its  loss  of  strength  might  remain  undetected  un- 
til, some  day,  the  structure  might  fall  under  its  ordi- 
nary working  load.  Fortunately,  much  evidence  is 
available  to  the  effect  that  steel  or  iron  thoroughly 


HOW  TO  USE  THEM 


507 


imbedded  in  concrete  is  permanently  protected  from 
rust.  Americans,  indeed,  are  so  positive  on  this  point 
that  they  have  recently  constructed  a  number  of  reser- 
voir dams  in  ferro-concrete.  In  some  cases  these  have 
been  arched,  but  in  others  they  have  been  straight. 
The  cross-section  in  the  latter  case  is  generally  a  hollow 
triangle^  the  sides  of  which  are  connected  together  by 
diaphragm  walls  from  point  to  point.  The  dam  is  also 
anchored  to  its  site^  though  generally  the  weight  pro- 
vided is  sufficient  to  make  the  structure  safe  against 
overturning,  quite  apart  from  the  help  received  from 
the  anchor-bars. 

Progress  in  the  use  of  reinforced  concrete  has  been 
somewhat  slow  in  England.  The  railway  engineers,  in 
view  of  their  enormous  responsibilities,  have  not  un- 
naturally hesitated  to  adopt  a  material  in  which  it  was 
impossible  to  calculate  the  strength  with  accuracy,  and 
of  which  experience  as  to  its  reliability  was  very  re- 
cent.  In  the  larger  cities,  moreover,  its  use  has,  quite 
apart  from  this,  been  restricted  by  the  inelastic  na- 
ture of  the  building  regulations,  which  have  been 
reached  upon  the  assumption  that  finality  had  been 
reached  in  the  matter  of  building  construction.  Hence, 
permission  to  erect  warehouses  and  factories  in  ferro- 
concrete has  alwaj^s  been  difficult — and  often  impossi- 
ble— to  obtain,  though  experience  has  shown  that  the 
new  material  is  most  excellent  as  a  fire-resister.  At 
the  great  Baltimore  fire  it  was  found  that  the  concrete 
exposed  to  the  flames  was  seldom  damaged  to  a  greater 
depth  than  one-half  inch^  though  projecting  corners 
suffered  somewhat  more,  being  rounded  off  by  the 
flames  to  a  radius  of  about  two  inches,  pointing  to  the 
advisability  of  constructing  the  concrete  with  well- 


508  CEMENTS  AND  CONCRETES 


rounded  corners  in  the  first  instance.  The  only  rea- 
sonable grounds  of  objection  to  any  proposed  system 
of  building  construction  are  its  dangers  from  a  struc- 
tural sanitary  or  fire-risk  point  of  view.  As  a  result 
of  much  investigation  and  experiment,  the  following 
conclusions  were  arrived  at  for  the  guidance  of  the 
designer  and  constructor  of  reinforced  concrete : 

1.  AVhat  drawings  and  details  should  be  prepared 
before  work  is  commenced. 

2.  The  nature  of  the  materials  which  may  be  em- 
ployed and  the  standards  to  which  these  should  com- 
ply, i.  e., 

(a)  the  metal  in  reinforcement, 

(b)  the  matrix, 

(c)  the  sand, 

(d)  the  gravel,  stone,  clinker  or  other  aggregate, 

(e)  water. 

3.  What  are  the  proportions  for  concrete  to  be  used 
in  different  cases. 

4.  How  the  ingredients  for  concrete  are  to  be  mixed 
and  deposited  on  the  work. 

5.  The  distances  to  be  allowed  between  the  reinfor- 
cing bars  and  what  covering  of  concrete  is  necessary. 

6.  What  precautions  are  necessary  in  the  design  and 
erection  of  centring  and  false  work,  and  how  long  the 
whole  or  portion  of  centring  and  false  work  should  re- 
main in  position. 

7.  The  rules  which  should  be  used  in  determining 
the  dimensions  of  the  several  parts  necessary  for  secur- 
ity, and  what  safe  stresses  should  be  allowed. 

8.  The  supervision  necessary  and  the  special  matters 
to  which  it  should  be  directed. 


HOW  TO  USE  THEM 


509 


9.  The  fire-resisting  properties  of  reinforced  con- 
crete. 

10.  Its  adaptability  for  structures  where  resistance 
to  liquid  pressure  is  essential,  and  what  special  precau- 
tions may  be  advisable  under  these  conditions. 

11.  What  are  the  necessary  conditions  for  its  perma- 
nence; resistance  to  rusting  of  metal,  disintegration  of 
concrete  or  effects  of  vibration. 

12.  The  testing  of  the  materials  employed  and  of  the 
finished  structures. 

13.  What  provisions  are  desirable  in  Building  Laws 
or  Government  regulations  relating  to  buildings  and 
other  structures  so  far  as  these  affect  the  use  of  rein- 
forced concrete. 


INDEX 


PA6B 

MATERIALS : 

Limes   27 

Cements    30 

Mortars    28 

Sand    28 

Plasters  and  laths   31 

WORKMANSHIP: 

External  work    35 

Internal  work   37 

SPECIFICATION  CLAUSES: 

Materials    42 

Workmanship    43 

PREPARATION  OF  BILL  OF  QUANTITIES: 

Materials   46 

Workmanship    46 

Laths   48 

TOOLS  AND  APPLIANCES : 

Hoes  and  drags   50 

The  hawk   52 

The  mortar  board  ,  o . . .  .  52 

Trowels    52 

Floats    52 

Moulds   54 

The  pointer   54 

The  paddle    55 

Stopping  and  picking  out  tools   55 

Mitering  rod   55 

Scratcher   55 

511 


512  INDEX 

PAGti 

TOOLS  AND  APPLIANCES.— Continued, 

Hod    55 

Sieve   56 

Sand  screens    56 

Mortar  beds   57 

Slack  box   57 

Lathing    57 

Lather's  hatchet   58 

Nail  pocket    58 

Cut-off  saw   58 

PLASTER,  LIME,  CEMENTS,  SAND,  ETC.: 

Plaster  of  Paris   60 

Quick  and  slow  setting  plaster   62 

Testing   63 

French  plaster   65 

Limes    65 

Hydraulic  limes    66 

Calcination   69 

Slaking   :   70 

Mortar    73 

Hardening  of  mortar.  .   78 

Magnesia  in  mortars   82 

Effects  of  salt  and  frost  in  mortar   84 

Sugar  with  cement   86 

Sugar  in  mortar   88 

Lime  putty    89 

Setting  stuff                                                 .  90 

Haired  putty  setting   91 

Lime  water    91 

Hair   91 

Fibrous  substitutes  for  hair   92 

Sawdust  as  a  substitute  for  hair   93 

Sand   94 

Mastic   96 

Scotch  mastic   96 

Common  mastic   97 

Mastic  manipulation   „   97 


INDEX  513 

PAGE 

PLASTER,  LIME,  CEMENT,  ETC.— Continued. 

Hamelein's  mastic    97 

Mastic  cement    98 

TERMS  AND  PROCESSES: 

Three-coat  work   99 

First  coating   99 

Scratching  ; .  100 

Rendering   •   102 

Screeds   103 

Floating   103 

Flanking   106 

Scouring  coarse  stuff   Ill 

Keying    112 

Setting    114 

Laying  setting  stuff   115 

Scouring  setting  stuff   115 

Troweling  and  brushing  setting  stuff   116 

General  remarks  on  setting   117 

Common  setting    119 

Skimming    119 

Colored  setting   119 

Gauged  setting   120 

Gauged  putty  set   120 

Putty  set   121 

Internal  angles   121 

External  angles   121 

Skirtings     122 

Two  coat  work   123 

One-and-a-half  coat  work   123 

Stucco    124 

Old  stucco   124 

Common  stucco    129 

Rough  stucco    129 

Bastard  stucco    130 

Troweled  stucco   130 

Colored  stucco   131 

Method  of  working  cements   131 


514  INDEX 

PAGE 

TERMS  AND  PROCESSES.— Continued. 

White  cement  efflorescence   138 

Cornice  brackets   139 

Cornices   140 

Mitring   155 

Mitre  mould    156 

Fixing"  enrichments   159 

Mitring  enrichments                                       .  160 

Pugging    163 

Sound  ceilings    164 

Cracked  plaster  work   165 

Repairing  old  plaster  ,   165 

Gauged  work   168 

Joist  lines  on  ceilings   169 

Rough  casting    170  . 

VARIOUS  METHODS  OF  RUNNING  COR- 
NICES, CIRCLES,  ELLIPSES  AND  OTHER 
ORNAMENTAL  STUCCO  WORK: 

Diminished  columns    177 

Column  trammel    180 

Constructing  plain  diminished  columns   183 

To  set  out  the  flutes  of  diminished  columns.  .  .  .  183 

Constructing  diminished  fluted  columns   185 

Forming  diminished  fluted  column  by  the  rim 

method    193 

Running  diminished  fluted  column  by  the  Col- 
lar method    196 

Diminished  fluted  pilasters   200 

Pannelled  coves    200 

Diminished  mouldings   204 

False  screed  method   204 

Running  double  diminished  mouldings   208 

Diminished  rule  method   208 

Top  rule  method   211 

Cupola  panels  and  mouldings   215 

Panelled  beams   220 


INDEX  515 

PAGE 

VARIOUS  METHODS,  ETC.— Continued. 

Trammels  for  elliptical  mouldings   220 

Templates  for  elliptical  mouldings   224 

Plasterer's  oval    228 

Coved  ceilings   233 

Circle  mouldings  on  circular  surfaces   233 

Forming  niches    235 

Running  an  elliptical  moulding  in  situ   240 

MISCELLANEOUS  MATTERS: 

Depeter    243 

Sgraffitto    243 

Fresco   f   251 

Fresco  seeco    255 

Indian  fresco  and. marble  plaster   256 

Scagliolia    260 

Artificial  marbles   262 

Pick's  neoplaster    263 

Scagliolia  manufacture    264 

Mixing    270 

Colors  and  quantities   272 

Polishing  white  scagliolia   275 

Polishing  scagliolia    276 

Marezzo    277 

Granite  finish   282 

Granite  plastering  .   283 

CEMENTS  AND  CONCRETES  AND  HOW  TO 

USE  THEM: 

Fine  concrete   291 

Matrix    293 

Aggregate   294 

Porous  aggregates   295 

Compound  aggregates   .  296 

Sand  and  cement   297 

Fire-proof  aggregates   300 

Voids  in  aggregates   302 

Crushing  strength  of  concrete   302 


516  INDEX 

PAGE 

CEMENTS  AND  CONCRETES.— Continued. 

Water  for  concrete.   303 

Gauging  concrete   305 

Ramming  concrete   308 

Thickness  of  concrete  paving   309 

Concrete  paving   310 

Eureka  paving   312 

Eureka  aggregate   313 

Eureka  quantities   314 

Levels  and  falls   315 

Pavement  foundations   316 

Screeds  and  sections   318 

Laying  concrete  pavements   320 

Troweling  concrete  .   321 

Grouting    322 

Dusting   322 

Temperature   322 

Non-slippery  pavements   323 

Grooves  and  roughened  surfaces   323 

Stamped  concrete    325 

Expansion  joints   325 

Washing  yards   328 

Stable  pavements   328 

Concrete  slab  moulds   329 

Slab  making   330 

Induration  concrete  slabs   330 

Mosaic   331 

Concrete  mosaic  ,   333 

Concrete  mosaic  laid  in  situ.   334 

Storing  cement   .   337 

Cement  mortar   337 

Mixing   338 

Grout    339 

Lime  and  cement  mortar.   339 

Cement  mortar  for  plastering   339 

Materials  for  making  concrete  sand   340 

Gravel   341 


INDEX  517 

PAGE 

CEMENTS  AND  CONCRETES.—Continued. 

Crushed  stone   341 

Stone  verOTs  gravel   342 

Cinders    342 

Concrete    343 

Proportioning  materials    344 

Aggregate  containing  fine  material   345 

Mechanical  mixers   346 

Mixing  by  hand.  .   346 

Consistency  of  concrete   347 

Use  of  quick  setting  cement   347 

Coloring  cement  work   347 

Depositing  concrete   348 

Retempering    349 

Concrete  exposed  to  sea-water   349 

Concrete  work  in  freezing  weather   350 

Rubble  concrete   350 

To  face  concrete   351 

Wood  for  forms   352 

Concrete  sidewalks   352 

Excavation  and  preparation  of  subgrade   353 

The  subf  oundation   353 

The  foundation   353 

The  top  dressing  or  wearing  surface   354 

Details  of  construction   384 

Concrete  basement  floors   358 

Concrete  stable  floors  and  driveways   358 

Concrete  steps    359 

Reinforced  concrete  fence  posts   360 

Reinforcement   362 

Concrete  for  fence  posts   362 

Molds  for  fence  posts   363 

Attaching  fence  wire  to  posts   365 

Molding  and  curing  posts   365 

Concrete  building  blocks  ,   368 

Tests  of  concrete  fence  posts   370 

Retempering   \   378 


518  INDEX 

PAGE 

CEMENTS  AND  CONCRETES.— Continued. 

Some  practical  notes   380 

Concrete  stairway  and  steps   387 

Cast  concrete  stairs   389 

Test  of  steps   390 

Concrete  stairs  formed  in  situ   391 

Setting  out  old  stairs   391 

Nosings  and  risers   392 

Framing  staircases    394 

Centring  for  landings  and  soffits   396 

Waterproof  centring   397 

Staircase  materials    399 

Filling  in  stairs   400 

Finishing  stairs   404 

Non-slippery  steps   405 

Striking  centrings    405 

Concrete  and  iron.   406 

Setting  concrete  soffits   408 

Fibrous  concrete   408 

Polished  soffits    409 

Concrete  staircases  and  fibrous  plaster   410 

Dowel  holes   410 

Cast  steps   411 

Treads  and  risers   412 

Closed  outer  strings   413 

Conciete  floors    413 

Plaster  floors   415 

Joist  concrete  floors   416 

Caminus  concrete  cement   417 

Concrete  floors  and  coffered  ceilings   418 

Combined  concrete  floors  and  panelled  ceilings .  419 

Concrete  and  wood   420 

Concrete  drying   421 

Concrete  slab  floors   423 

Construction  of  slab  floors   425 

Hollow  floors    427 

Concrete  roofs   428 


INDEX  519 

PAGE 

CEMENTS  AND  CONCRETES. —Continued. 

Notes  on  concrete   429 

Cast  concrete    431 

Concrete  dressing    432 

Mouldings  cast  in  situ   438 

Modelling  in  fine  concrete   443 

Concrete  fountains   446 

Concrete  tanks   44S 

Concrete  sinks   443 

Garden  edging    443 

Concrete  vases   448 

Concrete  mantel  pieces   449 

Colored  concrete   449 

Fixing  blocks    452 

Typical  system  of  reinforced  concrete  construc- 
tions from  various  sources   452 

Columns  and  piles   458 

Floors,  slabs  and  roofs   468 

Beams   469 

Arches   471 

Lintels   473 

Concrete  walls    475 

Strong  rooms  .   475 

Concrete  coffins  and  cementation   475 

Tile  fixing   477 

Setting  floor  and  wall  file  ,  ,  479 

Foundations   479 

Lime  mortar  .   .  480 

Concrete   480 

For  floors   480 

For  wood  floors   483 

In  old  buildings   481 

For  hearths   "   48"? 

For  walls    484 

Cement   486 

Sand   486 

Mortar  .......  486 


INDEX 


PAGE 

CEMENTS  AND  CONCRETES.— Continued. 

Soaking   486 

Tiles  for  floors   486 

Ceramics    488 

Files  for  walls  and  wainscoting  490 

Floating  wall  tile   491 

Buttering  wall  tiles   491 

Hearth  and  facing  tile   492 

Cleaning  492 

Cutting  of  tile   492 

Tools   492 

Laying  tile  on  wood   493 

Good  concrete   495 

Reinforced  concrete   500 


NOTICE 

To  the  many  workmen  who  are  purchasing  the  publications  under  the 
authorship  of  Fred  T.  Hodgson,  and  who  we  feel  sure  have  been  benefited 
by  his  excellent  treatises  on  many  Carpentry  and  Building  subjects,  we 
desire  to  inform  them  that  the  following  list  of  books  have  been  published 
since  1903,  thereby  making  them  strictly  up-to-date  in  every  detail.  All  of 
the  newer  books  bearing  the  imprint  of  Frederick  J.  Drake  &  Co.  are  modern 
in  every  respect  and  of  a  purely  self -educational  character,  expressly  isslied 
for  Home  Study. 

PRACTICAL  USES  OF  THE  STEEL  SQUARE,  two  volumes,  over  500 
pages,  Including  100  perspective  views  and  floor  plans  of  medium- 
priced  houses.    Cloth,  two  volumes,  price  $2.00.    Half  leather. - 
price  $3.00. 

MODERN  CARPENTRY  AND  JOINERY,  300  pages,  including  50  house 
plans,  perspective  views  and  floor  plans  of  medium  and  low-cost 
houses.   Cloth,  price  $1.00.   Half  leather,  price  $1.60. 

BUILDERS'   ARCHITECTURAL  DRAWING   SELF-TAUGHT,  over  350 

pages,  including  50  house  plans.  Cloth,  price  $2.00.  Half  leather, 
price  $3.00. 

MODERN  ESTIMATOR  AND  CONTRACTORS'  GUIDE,  for  pricing  build- 
ers'  work,  350  pages,  including  50  house  plans.  Cloth,  price  $1.50. 
Half  leather,  price  $2.00. 

MODERN  LOW-COST  AMERICAN  HOMES,  over  200  pages.  Cloth,  price 
$1.00.   Half  leather,  price  $1.50. 

PRACTICAL  UP-TO-DATE  HARDWOOD  FINISHER,  over  300  pages. 
Cloth,  price  $1.00.   Half  Leather,  price  $1.50. 

COMMON  SENSE  STAIR  BUILDING  AND  HANDRAILING,  over  250 
pages,  including  perspective  views  and  floor  plans  of  50  medium-priced 
houses.   Cloth,  price  $1.00.   Half  leather,  price  $1.50. 

STONEMASONS'  AND  BRICKLAYERS'  GUIDE,  over  200  pages.  Cloth, 
price  $1.50.   Half  leather,  price  $2.00. 

PRACTICAL  WOOD  CARVING,  over  200  pages.  Cloth,  price  $1.50.  Half 
leather,  price  $2.00. 

Sold  by  booksellers  generally,  or  sent,  all  charges  paid,  upon  receipt  of 
price,  to  any  address  in  the  world 

FREDERICK  J.  DRAKE  &  CO. 

Publishers 
CHICAGO,    :      :      :      ;    U.  S.  A. 


JfIMm  Carpentry  y 

ADVANCED  SERIES 

'  Bjj  jf  red  2,  ibodgson  == 

This  is  a  continuation  of  Mr.  Hodgson's  first  volume  on  Modern 
Carpentry  and  is  intended  to  carry  the  student  to  a  higher  plane 
than  is  reached  by  the  first  volume.    The  first  volume  of  this  series 

may  be  considered  as  the  al- 
phabet of  the  science  of  car- 
pentry and  joinery,  v^hile  the 
present  volume  leads  the  stu- 
dent into  the  intricacies  of  the 
art  and  shows  how  certain 
difficult  problems  may  be  solved 
with  a  minimum  of  labor. 
Every  progressive  workman — 
and  especially  those  who  have 
purchased  the  first  volume  of 
this  series — cannot  afford  to  be 
without  this  volume,  as  it  con- 
tains so  many  things  necessary 
the  advanced  workman  should 
know,  and  that  is  likely  to  crop 
up  at  any  time  during  his  daily 
labors.  The  work  is  well  illustrated  with  over  1 00  diagrams,  sketches 
and  scale  drawings  which  are  fully  described  and  explained  in  the 
text.  Many  puzzling  working  problems  are  shown,  described  and 
solved.  This  is  truly  a  valuable  aid  and  assistant  for  the  progressive 
workman. 

300  pages,  fully  illustrated.    12mo,  cloth,  price,  $1.00 

Sold  by  Booksellers  generally  or  sent  postpaid  to 
any  address  upon  receipt  of  price  by  the  Publishers 

FREDERICK  J.  DRAKE  &  CO. 

PUBLISHERS  CHICAGO,  U.  S.  A. 


Cnnlrartor  0  (^nxtit 


TO  CORRECT  MEASUREMENTS  of  areas  and 
cubic  contents  in  all  matters  relating  to  buildings  of  any 
kind.  Illustrated  with  numerous  diagrams,  sketches  and 
examples  showing  how  various  and  intricate  measure- 
ments should  be  takf^n    ::    ::    ::    ::    ::    ::    ::    ::  :: 

By  Fred  T.  Hodgson,  Architect,  and  W.  N.  Brown,  C.£.  and  Quantity  Surveyor 


7|THIS  is  a  real  practical  book, 
^  showing  how  all  kinds  of 
odd,  crooked  and  difficult  meas- 
urements may  be  taken  to 
secure  correct  results.  This 
work  in  no  way  conflicts  with 
any  work  on  estimating  as  it 
does  not  give  prices,  neither 
does  it  attempt  to  deal  with 
questions  of  labor  or  estimate 
how  much  the  execution  of  cer- 
tain works  will  cost.  It  simply 
deals  with  the  questions  of 
areas  and  cubic  contents  of  any 
given  work  and  shows  how 
their  areas  and  contents  may 
readily  be  obtained,  and  fur- 
nishes for  the  regular  estimator 
the  data  upon  which  he  .can 
base  his  prices.  In  fact,  the 
work  is  a  great  aid  and  assist- 
ant to  the  regular  estimator 
and  of  inestimable  value  to  the 
general  builder  and  contractor. 


12mo,  cloth,  300  pages,  fully  illustrated,  price    -  $1.50 

Sold  by  Booksellers  generally  or  sent  postpaid  to 
any  address  upon  receipt  of  price  by  the  Publishers 

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PUBLISHERS  CHICAGO,  U.S.A. 


STEEL  SQUARE 

A  TREATISE  OF  THE  PRAGTiOAL  USES  OF 

By  FRED.  T.  HODGSON,  Architect. 


New  and  up-to-date. 


Do  not  mistake  this  edition  for  the  one  published 
over  twenty  years  ago. 


This  is  the  latest  practical  work  om 

the  Steel  Square  and  its  uses  pub- 
ished.  It  is  thorough,  accurate,  cleai 
and  easily  understood.  Confounding 
terms  and  phrases  have  been  relig- 
iously avoided  where  possible, 
and  everything  in  the  book  has  been 
made  so  plain  that  a  boy  twelve  years 
of  age,  possessing  ordinary  intelli- 
gence, can  understand  it  from  begin- 
ning to  end. 

It  is  an  exhaustive  work  including 
some  very  ingenious  devices  for  laying 
out  bevels  for  rafters,  braces  and  other 
inclined  work;  also  chapters  on  the 
Square  as  a  calculating  machine,  show- 
ing how  to  measure  Solids,  Surfacea 
and  Distances— very  useful  to  builders 
and  estimators.  Chapters  on  roofing 
and  how  to  form  them  by  the  aid  or 
the  Square.  Octagon,  Hexagon,  Hip 
and  other  roofs  are  shown  and  ex- 
plained, and  the  manner  of  getting 
tho  rafters  and  jacks  given.  Chapters 
on  heavy  timber  framing,  showing  how 
the  Square  is  used  for  laying  out  Mor» 
tises,  Tenons,  Shoulders,  Inclined 
Work,  Angle  Corners  and  similai 
work.  The  work  also  contains  a  large  number  of  diagrams,  showing  how 
the  Square  may  be  used  in  finding  Bevels,  Angles ,  Stair  Treads  and  bevel 
cuts  for  Hip,  valley,  Jack  and  other  Rafters,  besides  methods  for  laying 
out  Stair  Strings,  Stair  Carriages  and  Timber  Structures  generally.  Also 
contains  26  beautiful  halftone  illustrations  of  the  perspective  and  fioor  plana 
of  25  medium  priced  houses. 

The  work  abounds  with  hundreds  of  fine  illustrations  and  explana* 
tory  diagrams  which  will  prove  a  perfect  mine  of  instruction  for  th« 
mechanic,  young  or  old. 

Two  large  volumes,  660  pages,  nearly  600  illustrations,  printed  on  • 
superior  quality  of  paper  from  new  large  type. 

Price,  2  Vols.,  cloth  binding  o  $2M 

Price,  2  Vols.,  half-leather  binding  3.00 

Single  Volumes,  Part  I,  cloth  l.OG 

p^rt  1  .half-  leather  «,   1 .50 

Part  II,  cloth   l.or 


Part II,  one  half-leather. 


i.oa 


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FREDERICK   J.  DRAKE  ®. 

PUBLISHERS  OF  SELF-EDUCATIONAL  BOOKS 
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THE) 

UP=TO=DATE 
HARDWOOD 
FINISHER 

IN  TWO  PARTS 

By  FRED  T.  HODGSON,  Architect 

Member  of  Ontario  Association  of  Architects^ 
Editor  of ''  National  Builder and  author  of  the 
''Modern  Estimator  and  Contractors'*  Guide,^^ 
''Modern  Carpentry,''*  "Architectural  Drawing 
Self-Taughtr  ''^Practical  Uses  of  the  Steel 
Square,^''  etc, 

PART  ONE,  giving  rules  and  methods  for  working  hardwoods,  with 
description  of  tools  required,  the  methods  of  using,  and  how  to 
sharpen  and  care  for  them,  including  saws,  planes,  files,  scrapers, 
chisels,  gouges  and  other  wood- worliing  tools.  How  to  choose  hard- 
woods for  various  purposes,  and  how  to  worit  and  properly  manage 
veneers.  The  proper  use  of  glue,  directions  for  preparing  glue,  blind 
or  secret  nailing,  how  done  and  how  finished.  How  to  sliarpen 
and  use  scrapers  of  various  forms,  with  illustrations  showing  the 
tools  and  how  to  handle  them  properly,  etc. 

PART  TWO  treats  on  the  filling,  staining,  varnishing,  polishing, 
gilding  and  enameling  woodwork  of  all  kinds  of  woods.  It  also 
treats  on  renovating  old  work,  repolishing,  re  varnishing  and 
wood-finishing  generally.  There  is  a  short  treatise  en  dyeing  woods 
in  various  colors  for  inlaying  and  marquetry  work,  with  rules  for 
making  staining,  dyes,  fillers,  and  polishes  of  various  kinds,  French 
polishing,  hard-oil  finish,  rubbed  and  flat  finish,  treatment  of  hard- 
wood floors,  waxing,  polishing,  shellacking  and  general  finishing  of 
hardwood  in  all  conditions. 


LARGE  12M0  CLOTH,  320  PAGES,  117  ILLUSTRATIONS.  PRICE,  $1.00 
HALF  LEATHER  BINDING,  GILT  TOPS       •       .       PRICE.  $1.50 

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PRACTICAL  BUNGALOWS 
AND  COTTAGES  FOR 
TOWN  AND  COUNTRY 


THIS  BOOK  CONTAINS  PERSPECTIVE 
DRAWINGS  AND  FLOOR  PLANS 


OF  ONE  HUNDRED  LOW  AND  MEDIUM  PRICED  HOUSES 
RANGING  FROM  FOUR  HUNDRED  TO  FOUR  THOUSAND 
DOLLARS  EACH.  ALSO  TWENTY-FIVE  SELECTED 
DESIGNS  OF  BUNGALOWS  FOR  SUMMER  AND  COUNTRY 
HOMES,  FURNISHING  THE  PROSPECTIVE  BUILDER 
WITH  MANY  NEW  AND  UP-TO-DATE  IDEAS  AND  SUG- 
GESTIONS IN  MODERN  ARCHITECTURE  

THE  HOUSES  ADVERTISED  IN  THIS  BOOK  ARE  EN- 
TIRELY DIFFERENT  IN  STYLE  FROM  THOSE  SHOWN 
IN   HODGSON'S  LOW   COST  HOMES  

12  MO.  CLOTH,  200  PAGES,  300  ILLUSTRATIONS 
PRICE,  POSTPAID  $1.00 


FREDERICK  J.  DRAKE  &  CO. 


CHICAGO 


1bot 

Steam 
and  6as 


By  WM.  DONJiLDSON 


A MODERN  treatise  on  Hot  Water,  Steam  and  Furnace 
Heating,  and  Steam  and  Gas  Fitting,  which  is  in- 
tended for  the  use  and  information  of  the  owners  of  build- 
ings and  the  mechanics  who  install  the  heating  plants  in 
them.  It  gives  full  and  concise  information  with  regard 
to  Sieam  Boilers  and  Water  Heaters  and  Furnaces,  Pipe 
Systems  for  Steam  and  Hot  Water  Plants,  Radiation,  Radi- 
ator Valves  and  connections.  Systems  of  Radiation,  Heating 
Surfaces,  Pipe  and  Pipe  Fittings,  Damper  Regulators,  Fit- 
ters' Tools,  Heating  Surface  of  Pipes,  Installing  a  Heating 
Plant  and  Specifications.  Plans  and  Elevations  of  Steam 
and  Hot  Water  Heating  Plants  are  shown  and  all  other  sub- 
jects in  the  book  are  fully  illustrated. 

256  pages,  121  illustrations,  12 mo,  cloth,  price,  $1,50 

Sold  by  Booksellers  generally  or  sent  postpaid  to 
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Practical 
llp-to-Date 
PLUMBING 

By 

George  B.  Clow 

Over  150 
Illustrations 


A PRACTICAL  up-to-date  work  on  Sanitary  Plumbing,  com- 
prising useful  information  on  the  wiping  and  soldering  of 
lead  pipe  joints  and  the  installation  of  hot  and  cold  water  and 
drainage  systems  into  modern  residences.  Including  the 
gravity  tank  supply  and  cylinder  and  tank  system  of  water 
heating  and  the  pressure  cylinder  system  of  water  heating. 
Connections  for  bath  tub.  Connections  for  water .  closet. 
Connections  for  laundry  tubs.  Connections  for  wash-bowl  or 
lavatory.  A  modern  bath  room.  Bath  tubs.  Lavatories. 
Closets.  Urinals.  Laundry  tubs.  Shower  baths.  Toilet 
room  in  office  buildings.  Sinks.  Faucets.  Bibb-cocks.  Soil- 
pipe  fittings.  Drainage  fittings.  Plumber's  tool  kit,  etc.,  etc 
256  pages,  180  illustrations. 

12  Mo.  Cloth  .       c  $1.50 


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